Yes, websites do exist that will give you this information for free. However, much of the Mac is not about simply obtaining information. It's about how you get it. Xconvert provides a number of advantages in this regard.

1) Rates are cached so that they can be used without a connection to the internet.

2) Alerts inform you when rates have become outdated so you can update them for greatest accuracy.

3) Quick searching gives you the information you need as fast as possible.

4) The interface is streamlined to give you the results you need, when you need them.

5) Xconvert integrates excellently with the rest of your Mac-based workflow.

So, if you want information only, use the internet. But, if you want a complete solution, try Xconvert.

http://www.xe.com/ucc/

Apple's Conversion widget supports a number of popular currencies, and I'm sure there are dozens of websites available for more obscure currencies (xe.com comes to mind), so why would anyone pay six bucks for this?