I am supporting a number of .Net developers who are using Subversion to version control their work, but we have been running into a number of issues that seem to revolve aro
I think a better question would be "What files should I add to Subversion?"
The AnkhSVN 2.0 Subversion integration asks exactly this question to all the projects in your solution. (This question is one of the key parts of the SCC specification.) It will then only suggest adding these files.
As user you can add other files manually (or mark some of the files suggested as ignored), but this behavior makes it very easy to do the right thing.
Most other subversion clients don't have the luxury of talking to a system that really understands what should and shouldn't be added. (E.g. External clients like TortoiseSVN and its frontends can just guess based on file extensions).