Malici0us
http://www.declan-software.com/japanese_ime/
Microsoft IME is what I use. I'm not aware of any others out there.
And since I'm actually posting, would it be possible for someone to tell me how to type a chouon "ー" character, and " ・・・・" using Microsoft IME? I had to copy and past those because I just CAN NOT figure out how to type them out.
I just use a dash (-) for it, it looks about right in the IME. As for the ..., just type in "..." and hit space. Hitting space once or twice should convert it over.