Rdbhost currently provides a sandbox with the Stack Overflow dump data. It uses the PostgreSQL engine, and thus PostgreSQL syntax for SQL.
There is a PhpMinAdmin-type web-interface for manipulating the database. There is also a Python DB API module. The DB API module is described on our site, as well as an intro on using SQLAlchemy to access SO data.
If you have any problems with it, please let me know at email@example.com.
Update, June 8: The data dump account on has been updated again yesterday with the June 1st data dump.