i did work on an open source J2ME api(BIZU ME) and stopped when I started working full time. I can say that sourceforge is ok for hosting since that is what I used for hosting and had no problems what so ever. The UI is weird to deal with but its alright once u get used to it. I haven't tried any other such as google code etc so I cant give u any feedback on those.. You will probably need a bug tracking tool such as jira for tracking your issues. Jira is really good and offers a free licence if your project is open source. Apart from that , you will need weekly updates or else people lose interest pretty quickly!