I've been using MySQL with VB.net for awhile now. Basically all you need is a data provider for MySQL and you can treat it the same as you would a SQL Server database. In fact, if you design your app right it would be trivial to switch to whatever type of database you decide to use. Take a look here
for more information and to download a free data provider for use with MySQL.
Post back if you have any problems.
Wally
www.power-coder.net