I could use Campsites to...

Keep in touch with my coursemates

Prepare for a friend's birthday party

Organize a local community volunteering event

Prepare for exams with my study group

Plan the meetings of our book club

Move to a new place

Arrange a weekly barbecue

Stay in touch with a group of friends

Collaborate on an open-source project

Keep a private life log

Run an online community

Share favorite recipes with friends

Start a music band

...and much more!