Google's research group developed its own statistical translation system for the language pairs now available on Google Translate. To quote what they say the program does:
Our system takes a different approach: we feed the computer billions of words of text, both monolingual text in the target language, and aligned text consisting of examples of human translations between the languages. We then apply statistical learning techniques to build a translation model. We've achieved very good results in research evaluations.You can also install Google Translate on you iGoogle page and have it always ready, like a desktop application. I tried a test translation of the German Website page on Genealogy.net. The translation was reasonably accurate and very useful.
I don't make any claims as to the accuracy of the program, but it certainly cuts down on my search for dictionaries. If you want a lot of information about the program go to the About page with its Frequently Asked Questions.
There are plenty of other programs out there that do translation, such as Yahoo Babel Fish, (I didn't think the translation of the target German page was as helpful as Google Translate) but a lot of them are lead-ins to commercial programs. If you have a favorite, send it in and I will give it a try.