There are some neat little sites springing up that use OpenID for authentication. Check these out:
- Doxory: ask the world whether you should do X or Y
- Stuffopolis: Lend your stuff and keep track of who you've lent it to
- I Make Mistakes: Read about mistakes other people have made, rate them and post your own
There's lots of good, simple ideas out there. OpenID has the potential to act as a part of the glue could bind them together, too.