Working in front of the computer has taught me this about using online tools: while there are certainly a lot of them, I find that I only use a handful of the most useful ones every day.

Online tools are wonderful and they certainly are time savers. The hard part is to wade through hundreds of them to find that one gem. So, to help you save time, here is a list of the 10 Most Useful Online Tools Ever:

1. Google as Calculator, Unit Conversion, Currency Conversion and Translator

I know, I know - everyone already knows about Google. While it's certainly a popular search engine, did you know that you can use Google to do math, convert units of measurements, and even translate one language into another? I use Google for exactly these purposes every day:

• Google as Calculator
  Enter what you'd like to calculate in Google's search box as you would a regular calculator. For example:
  
  3x6=
  200/15=
  ((50+9)/45)-(9/5)=
  (sqrt 10)^5=
  
  You can do both simple arithmetic and advanced math. Google Guide has a neat article explaining all of the math functions built into Google's calculator
• Google as Unit Conversion
  Need to convert one unit of measurement into another? Just ask Google:
  
  yard to inch OR yard in inch*
  meter to feet OR meter in feet
  kg to lbs
  
  You can even do math conversion. For example:
  
  5 yards to inch
  2 days to seconds
• Google as Currency Conversion
  The same goes for currency. Simply query Google:
  
  USD to GBP
  Dollar to pound
  5 EUR to USD
• Google as Translator
  This one is pretty neat: Google Translate
  
  You can enter a word, a block of text or even a URL and have Google translate it from one of 51 languages supported into another. You can even have Google auto-detect the language!

What's even better is to do these without ever going to Google.com. If you select Google Search Engine Add-on for Firefox (it should come as a default), you can enter the query directly on the search box and the answer is displayed automatically right then and there. *A funny thing is that "yard to inch" doesn't work here, but "yard in inch" does.

2. Ta-Da List

Ta-Da is a very useful, easy to use - and best of all, free - online to-do list by the folks at 37signals. I use it every day to jot down tasks and ideas. You can even share your list with other people or make it public.

3. Creative Commons Search

Creative Commons Search is the easiest way to find creative commons- or CC-licensed images that you can use for your blog or website. Best of all, it is available as an add-on to Firefox.

Alternatively, you can also do CC license search directly in Flickr - simply check the "Only Search within Creative Commons-licensed content" at the bottom of the page.

Be sure to understand the various Creative Commons licenses - some require attributions, prohibit derivative works, and allows only non-commercial use of the image.

4. Clipart.com

Sometimes, you simply can't find the appropriate free image for your blog or website using Creative Commons Search. There are a lot of stock photo websites, but I find the most cost-effective one is clipart.com. For $34.95 a month or $159.95 per year (that's just $13.33 per month), you have an unlimited access to 10+ million royalty-free cliparts, photos, and illustrations.

The downside of clipart.com is that their photo quality is rather poor when compared to other stock photo websites. My other favorites are iStockPhoto and Dreamstime. In addition to buying a single image, they also offer subscriptions, but at a much higher price than clipart.com.

5. Dafont and What The Font

Need a free font? You can't go wrong with Dafont, where you can download free fonts (some are restricted to only personal use). The website classifies fonts according to various categories like calligraphy, decorative, typewriter, and dingbats. It will even display your phrase in various fonts so you can see exactly what they look like.

Ever seen a font that you like and want to know what it is? You can submit an image to MyFonts' cleverly named tool WhatTheFont! to identify it for you. This online tool is beta, and it doesn't always correctly identify the font, but at least it gives you useful alternatives even if it can't find the right one.

6. Down For Everyone or Just Me?

When I can't access my favorite websites or even my own blogs, I always wonder if it's the fault of my local ISP or whether the sites are actually down. The simplest way to check is by visiting Down For Everyone Or Just Me?

All you have to do is enter the domain name and it'll check for you.

7. Pandora

I don't know if you'd classify Pandora as an online tool - but the free Internet radio is so useful for finding new music that I'll put it on this list. The best thing about Pandora is that you can personalize it to play only the music you like.

In 2000, Will Glaser, John Kraft and Tim Westergren started the Music Genome Project to classify songs using a complex algorithm involving almost 400 attributes. A musician would analyze a particular song and classify it according to categories like "dominant use of harmony," "driving shuffle beat," "highly synthetic sonority" and so on. The idea is that if you like one song, then you should also like another one with similar musical qualities (or "genes," as they call them).

Today, the technology is used by Pandora - you can enter a particular song title or an artist's name, then it will create a special channel that - in theory - only plays similar music.

Unfortunately, due to licensing restrictions, you can only listen to Pandora if you're located in the USA. If that's the case, there's always YouTube where you can listen to music videos ...

8. Vector Magic

This one is rather obscure for non-designers, but I find it quite useful. Whenever I have to convert a bitmap image into vector art, I simply upload it to Vector Magic and voilà! - it's automatically done. In my experience, it's definitely worth the $7.95/month subscription, though you can try it for free first.

9. Cachefly

For a large-ish blog or website, you'll find this service very useful: a Content Delivery Network or CDN to host static files like images and media files. Putting these files on a CDN instead of your blog server helps reduce the load of your server. So instead of serving bulky images, your server can focus on delivering only small HTML files - thus greatly improving its performance.

Serving large image files from a CDN should also improve the page load speed for your readers. This is because most CDNs operate several nodes spread around the world. A reader in Europe would automatically be served from a nearby CDN server in Europe, rather than having to wait for the file to be delivered from, say, a server in the United States.

I use Cachefly, which caters to smaller companies. I find their setup (a regular FTP) easier than using other popular CDN services like Amazon's CloudFront or Simple Storage Service (S3).

10. Carbonite

The last tool here is actually the one I hope I never have to use. Carbonite is an online backup tool that automatically backs up files from your PC or Mac. It costs $54.95 per year, which is a bargain as compared to losing your files if your hard disk crashed (yes, there are services that fix broken HD, but those cost hundreds and hundreds and hundres of dollars).

The good thing about using an online backup service is that it's automatic. Sure you can do this by burning the content of your hard drive into a CD or a DVD, or copy it into an external hard disk, but when was the last time you did this? I thought so.

Having had a hard disk crash on me before, I can tell you this: it's a matter of when, not if. So whether you decide on using an online backup service (besides Carbonite, there are plenty of others like Mozy, though I haven't personally used them all) or an external hard drive (I do both, actually, just in case), please backup your computer today.

Lastly, a caveat: like I mentioned above, I haven't needed to use Carbonite's restore function. There are people who complain about their service, but I think the same goes for practically all online backup services.

Bonus: IronKey

Technically, this one isn't an online tool, but I find my IronKey to be so useful that I have to include it in this post somehow.

There are plenty cheaper USB or Flash drives, so why choose one that costs of more than $60 for a 1 GB drive? (I have the 8 GB version, about $170 from Amazon) The answer is simple: built-in encryption. IronKey is also waterproof, electromagnetically shielded, and darned near indestructible. Those features are nice (indeed, IronKey is military-grade), but I'm no James Bond ...

If you want to store sensitive personal data, this is the simplest way to do so. When you plug it into a standard USB socket, IronKey will ask for your password before letting you access the data. If it got stolen, and the thief entered the password wrong 10 times, the drive will automatically self-destruct and erase its content.

IronKey also offers private surfing using a built-in Firefox browser - but I find this to be too slow to use comfortably. Anyhow, Firefox 3 (and Microsoft Internet Explorer 8) now offers "Private Browsing" mode, so the point is rather moot.

Oh, and backing up your IronKey (while maintaining the encryption) onto your PC is also easy with a built-in function.

I'll be the first to admit that this list is too short - we didn't even talk about GMail, Google Docs, Microsoft Office Online, and Google Analytics. These are very popular tools and I thought that many of you'd already use them.

Got anything to add? Let's hear about 'em in the comment!