Well, there's one very interesting source control provider I found (SourceGear Vault) that provides at least a FREE one-user license! It is built entirely with .NET, and is backed by a SQL Server or MSDE database.
I use it at home, as I do not want to pay oodles of cash for these things.
It implements EVERYTHING that VSS does, minus the ability to check in/out files in the visual merge.
However, one thing that REALLY needs to be done with SCP integration, is supporting renaming of files/projects.. It really sucks when I want to move files to a different directory/sub-folder.. I do it locally, then must open VSS directly and move them as well.