Some ideas that I frequently wish existed:
1. It would be neat if there was some sort of place in Github where people could upvote interesting project ideas, i.e. "Load testing tool in Go"
2. I'd also love to have a way to say, "I can devote 1-5 hours a week to this project" and be notified when someone tags an issue as 'help wanted'
3. Harder, but still do-able (I think). A place for open sourcers to organize a "team" to get a new project off the ground. I often think that there _must_ be other people interested in the same sort of projects I am -- but we have no way to "discover" each other unless you're some high profile Twitter user.
4. Moderation for trolls. Some people frequently open issues that frustrate maintainers. While they can just create a new account, I think creating a small barrier to entry would do some good.
5. A way for companies / individuals / etc. to donate to maintainers through Github. I think this would be a huge incentive for people to continue their work long-term and not just "hand over" repositories to people with ulterior motives.