The following code will remove all the .svn folders from a tree (starting at the current file's directory).

Find.find(File.dirname(__FILE__)) { |path| `rm -rf #{path}` if path =~ /\.svn$/}

I've needed this enough times that I thought it might save someone else some time.

When did I use this? Every time I start a new project I check it into a local subversion repository. After working on the code for a bit, if I decide that it's a project worth distributing I register it somewhere else (such as RubyForge). If my project is accepted, I'll transfer the code to the projects repository. The easiest way, I've found, to move the code is to remove the local .svn directories and check out version 0 of the new repository into the project's root. At this point, I can svn add everything and check in.

I'm sure there's a better way, but this is simple and it works.