QuickBase(.com) may be something close to what you want: while mostly aimed at > 10 people businesses. It's not great, but it does have a reasonable amount of power... especially for apps with say less than 10 tables.

DabbleDB was a good one for individual users, until Twitter bought it and shut it down. Google says grovesite.com is a competitor... and I also think Dabble's founders were debating rewriting it.

There's always the old FileMaker Pro, or databases of that age / time. (4D??)