How, if it is possible, would you use VisualSVN to retrieve source code from an open source project (such as on codeplex), but also have your own SVN repository locally such that you could keep a revision history for your own customizations, but still once and a while check the codeplex project for changes that I might want to apply to my code. This particular project (on codeplex), I only have read-only access so I would never be checking code back up to to codeplex.
I am relatively new to VisualSVN, having only ever used Visual Source Safe in the past.
Is this type of setup even possible with the tools I have, and if not would another tool work? A few pointers would be a great help.
The SVN Book has a more thorough explanation than I could possibly give here, but the concept you're describing is vendor branches.
I'm not familiar with VisualSVN specifically, so I can't give you any step-by-step howto info; Perhaps someone else will be able to.