Google Translate now covers a huge range of languages, so for anyone working in a multi-lingual environment it's become a trusty tool.
goot is a cross platform translation tool that aims to harness this power conveniently on your desktop. It allows you to use plug-ins to integrate it with a huge number of online translators, the principle one being Google Translate (which is included by default). If you want a plug-in for a translation site that's not available, as long as you know a bit of Java you can make your own.
The big disadvantage of goot though is that it's only suitable for single words and sentences. It can't translate huge chunks of text or entire web pages. It does, however, auto-detect the language the source was written in, making it useful if you're constantly interchanging texts. Translations are generally very good and delivered quickly although it obviously depends on the plug-in you are using.
goot is a handy way to bring powerful translation tools to your desktop, although it's a shame it doesn't translate more than a few words at once.