pmono is a set of 32bit and 64bit debian pacakges for mono and monodevelop providing the most recent mono and monodevelop releases as a parallel mono environment that wont conflict with your existing mono installation.
Installing pmono is easy, simply add the following to your /etc/apt/sources.list file
deb http://void.printf.net/~bredroll/pmono ./
Now (as root) run the following:
$ apt-get update
$ apt-get install pmono-monodevelop pmono-scripts
Running Under pmono
This is fairly easy too thanks to the pmono script, you can prefix your mono command lines with it..
$ pmono monodevelop whatever.sln
$ pmono monodoc
$ pmono gmcs /?
$ pmono nunit-console my-test-assembly.dll
$ pmono csharp
..or source it into your shell environment like so:
$ source /usr/local/bin/pmono
$ mono --version