Do you use UML as a test or development environment? Perhaps you compile software in different environments, and use UML as your isolation mechanism.
GUML could be the tool you've been looking for. It provides a means to manage and run as many UML instances as you need, all in one handy location.
GUML is currently in a very early stage of development. It is usable, but is missing a number of useful features I'm hoping to add in the near future. Check the TODO file in the distribution for info on things I'm planning on adding.
Sorry, I don't have download locations for these, I just use the Debian packages python-gtk2 and python-vte. And so should you.
There should also be Debian packages available from the Debian archive (package name guml).
Current development is undertaken in GNU Arch using the Bazaar client. The current trunk of development is in the guml--trunk--0 branch of http://www.hezmatt.org/~mpalmer/arch/mpalmer@hezmatt.org--public-2004.
Questions? Comments? Bug reports? Patches? E-mail me at mpalmer@hezmatt.org.