There is a kit by aubreTEC that has everything you need to setup your own persistant off-world database for Second Life called SLDB (Second Life Data Base). All you need is a PHP/MySQL-equipped web hosting accout. No PHP or MySQL knoweledge required (but it helps).
The SLDB kit contains a web app (PHP scripts to setup and access the DB), LSL script and instructuoins. For tinkerers, It's open source so you can see what the scripts do and how they do it. For anyone who just wants to get a DB working, just follow the instructiuons, they are very good and can walk you through the process painlessly.
Oh, did I mention, it's FREE!!!!
It can be found here on the marketplace: SLDB by aubreTEC
Or you can get it right from the aubreTEC website: SLDB by aubreTEC