GNOME Launch Box is looking sweet. Well, at least from the screenshots, not that I've tried it yet. I was hacking in the autumn on something a bit similar; it's called Pepper but it sits abandoned for the moment. (For anyone interested, it's written in Python and available with tla at email@example.com/pepper--mainline--0.1, http://www.helsinki.fi/~pakaste/arch/) If the hack by the Imendio boys is any good, it can stay abandoned.
In other news, feeling that PyGTK is becoming mainstream, I seeked out a new ghetto and started hacking with λgtk and SBCL. λgtk is a bit painful to install at the moment, requiring a new core with the sbcl-af stuff for SBCL, but it looks like Brian Mastenbrook is working on it. I was thinking of using OCaml, but then decided that the type inference stuff of CMUCL/SBCL is good enough a compromise between decent typing and flexibility. If anything comes of this project, I'll probably have to take a look at the libglade bindings I pointed at previously and also bind gconf and stuff.
Also, in the category of nifty languages building on other people's VMs, yet another one I wasn't previously aware of: Nice doesn't look too bad. Also see Scala, Boo and Nemerle. For the record, I think Groovy looks like what happens when a dozen languages collide with each other and someone is picking up the pieces and trying to match them together. With little success.