I really like being able to find words/phrases in foreign languages when talking to people, and it's getting easier every day with the Internet's resources.
Here's a decent Thai dictionary … the entry for spam
The ngata dictionary for Maori is pretty good too … although it doesn't seem to have quite as much slang in it.
Freedict covers Latin and a few others, but it doesn't seem to be a very in-depth treatment, unfortunately.
And for English itself, we have the excellent Wordnet – which is often seen in Google search results, and is available as a local application for most OSs as well as an online resource. Go meronym, go hypernym, holonym and gloss :-)