Depending on your needs, there's quite a few foreign dictionaries available on the Internet that can be converted fairly easily to .mobi. A good resource for this is the StarDict project
For example, my default dictionary on the kindle right now is the XMLittré, a 19th Century French dictionary that works better than modern dictionaries for all the Dumas and de Maupassant I'm reading right now.
Dual-language (like French-English) dictionaries are a bit rarer, though. And, unfortunately, I don't really understand the copyright on a lot of this stuff well enough to feel comfortable posting conversions of them. For example, there's a bunch of free dual-language dictionaries at http://www.microsoft.com/reader/down...tionaries.aspx
, but I don't think conversions of them can be distributed.