This site is actually really easy to get started with and willing to let you study without bothering you.

Regarding the approach (type in a translation for the requested term), I am a bit sceptical. It seems to require that there is one unique translation for each term. Maybe multiple choice would be better? This would also solve the irritating keymap for foreign language problem (http://smart.fm solves this nicely with a custom input mechanism in flash).

I've tried Rosetta, smart.fm, others that score you based on your input, but by far the simplest and best method I've found is using Anki, which just asks you 'did you remember it?' and it's up to you to answer truthfully.

http://ichi2.net/anki/

There's more than one translation for words with synonyms (although people keep coming up with more synonyms).

And I use a custom js-based keymap that works on all os'es, and teach students how to enter accents.

Wow! Really nice job on that! I'm doing the English -> Spanish lessons, and it's really thoroughly made (it can tell me why something was wrong, if I was close, etc.) I really like the registration process. Play with the site for a bit, and then fill in a few fields to save your progress.