Mono – Configure Mono Version for MonoDevelop

Not sure it's the best option, but i use the repository of badgerports
About badgerports:

badgerports is a software repository for use with Ubuntu Linux 10.04. Whilst on the whole it is a good idea to use the software provided with your Linux distribution, there are sometimes bugs or major software updates that cannot be included for operational reasons. badgerports is a home for a number of wayward software packages, to enhance the Ubuntu experience.

The primary purpose of badgerports is to provide recent versions of the Mono framework, and associated packages such as F-Spot, Banshee, and Monodevelop. Suggestions for other packages to include are welcome, but don't be offended if I decline for whatever reason.whatever reason.

You can find the instructions on how to use it here

This is a somewhat vague answer, I know, but I hope it helps:

• Download the appropriate tarballs from http://ftp.novell.com/pub/mono/sources-stable/
• Follow the instructions for compiling at http://www.mono-project.com/Compiling_Mono_From_Tarball

The only dependencies listed on the latter page ARE NOT necessary for version 2.8, so you should (hopefully) have most everything you'll need already. But you're probably much more knowledgeable about this than I am, so hopefully the instructions there will give you all the info you need. Also, if you build from source, you shouldn't have any problems with the Ubuntu repo versions (unless you haven't completely uninstalled them already).

Good luck!