Innovative, open source email/contacts/calendar server and client. Lots of interesting looking integration between the calendar/email/etc. in the AJAXy browser client, and support for existing clients too. Plus the server could become the open source Ex
Kathy Sierra gives some good tips on getting picked as a speaker for conferences. Not something I'm aiming to do right now, but I quite fancy the idea sometime in the future - guess I'd need to find something to speak about first...