I'm always on the prowl for a possible transition from VFP and ran across the following. Interesting information on their websites and seems to be obvious contenders.

Alpha Five - uses dbf's natively, no runtime fees, potential to develop web apps as well.

Filemaker Pro - seems to be a lot of users and has a native database, free distribution of apps, lots of support.

Realbasic - cross platform, no runtime fees for single user versions.