Of course RVM is pretty much ubiquitous for managing multiple versions of Ruby on Linux and OS X, but what about all you Ruby folks on Windows? I just want to make sure you know about pik. Installing new versions is not quite as smooth an experience as RVM, but it's not bad, and the switching between versions experience is actually better than RVM, because it fuzzy-matches the version with what you type.
So if you've been itching to play around with Ruby 1.9.2 but you're still working on an app in 1.8.7, pik is your answer. And if you're still clinging to your Visual Studio and have not yet taken the plunge to see what all this Ruby buzz is about, by all means head over to rubyinstaller.org right now and get started. You won't regret it. The more Windows users on Ruby, the better.