A long time ago, I lauded Movable Type for supporting a variety of database backends. This feature allowed for a wide range of installation scenarios. Apparently this ability got lost in recent vintages of MT for the whizzy dynamic publishing capablities.
Anil Dash concurs with me (;-)) and reports that PostgreSQL and SQLite DBs can be used with dynamic publishing. Some of the GIS, XML, and extensibility features in PostgreSQL could be put to amazing effect for an enterprising MT extension hacker.