Here’s the list of the biggest community-based developer’s conferences in Japan. Please leave a comment if I forgot to mention your favorite conference.
YAPC::Asia Tokyo (Yet Another Perl Conference) had been held twice, and was very successful. YAPC officially adopts two languages (Japanese and English), and many speakers attended from different countries. Previously Audrey Tang from Taiwan, did a great talk on Haskell.
RubyKaigi 2008 will be held in Tsukuba on June 20th-22nd. English speakers are expected to talk. Here is the CFP. The deadline is 17th February. Previously David Heinemeier Hansson (Ruby on Rails developer), and Dave Thomas (author of Programming Ruby) gave keynotes.
Open Source Conferences
Open Source Conferences are held in many cities in Japan by Toru Miyahara, the president of a company called Begi.net. I’m not sure there was any English speaker in OSC before, but they may welcome English presentation or booth.