The ones I have installed (all free) are:
- Bible - great for searching for verses
- BoxOffice - great for finding showtimes near you
- Facebook - not that useful
- Travelocity - nice app, lets you see flight times, schedules, and security wait times
- LocalPicks - TripAdvisor app to find good restaurants near you.
- Google - Not that great, but quick access to lots of Google sites.
- BookSearch - Price comparison for books.
- Cellfire - Coupons for nearby stores (not much selection, though)
- Shazam - Identify songs.
- Flashlight - Use your iPhone as a flashlight.