Translate Net is an useful Open Source program that nowadays supports 22 online translation services, 35 languages and 1352 language combinations. The feature that makes me to find it extremely useful is that Translate Net is used right from desktop, so you don't have to go from one page to another to compare results.
The process is simple, install Translate NEt and it will remain in the system tray waiting for you to use it, once you need it you only have to click it, choose the pair of languages and insert the word or phrase you want to translate, press the translate button and it will automatically search for the translation of the word in the different online translation services and it will feature all of them on screen, so you can view them and choose the option you like the most.
Once you have used it once or twice it will create a profile automatically and will feature in the right-down side the most used pairs of languages, so it will be easier to access them.
If you usually visit foreign websites or if you are translating some documents, Translate.Net is really useful.
Windows 2000, XP, 2003, Windows Vista.