The DragonFly page on the Summer of Code site is set up. If you are a potential mentor that I’ve talked to before, I’ve already sent you an email with details. If you are a potential mentor I haven’t talked to, you can email me or send a request via the DragonFly page. (Google has a new ‘connections’ method for signup this year.)
If you’re an interested student, take a look at the DragonFly Projects Page. Keep in mind that your proposal does not have to be one of those ideas – new projects are always welcome, and often have the advantage of being unique instead of being one of several similar proposals. (hint, hint)