Bento alternative? Looking for databasing app for Mac that syncs easily between computers/users?

I have a small workgroup that needs to share and edit a database for a collaboration-based project; I have purchased a family pack of FileMaker’s Bento software, only to learn that it has poor inter-user support.

The idea is that I need to be able to sync the database easily between 3–5 users. Any recommendations?

Also I have heard that some people are having success with Google Apps (Google Docs) and syncing using a dropbox app of some sort?

Bonus if the app has import/export/sync with Entourage or iCal/Address Book, etc.

Any help is greatly appreciated-thanks in advance!