I myself like MySQL, and it seems to be a pretty powerful database. Other than that my only other experience is with Oracle, which is an awesome database if you have large amounts of data (we use this at my work place.)

However, what I have really liked about MySql is that its free! Does anyone know how much data a MySql database will hold before it starts to get sluggish? And does MSsql express have the ability to store more data?

I may have to give it a try since it is available for free.