I'm working through the lessons at Programmer’s Heaven's "C# School" tutorial (http://www.programmersheaven.com/2/Les_CSharp_0), and I'm currently on lesson 13, "Data Access in .Net using ADO.Net", so of course I've been trying to connect to Programmer’s Heaven's SQL and MS Access / OleDb databases. Unfortunately, they're now offline. Can anyone please tell me; are there other such databases available for those learning ADO to practice connecting to?

Just get SQL Server Express. It's free and should do everything you need for working through tutorials. I would recommend downloading SQL Server Management Studio Express as well (The express versions are the free ones).