In addition to the basic packages suggested by Matthew, you will also need a package monodevelop-nunitthat allows you to run and debug unit tests from the IDE. For the debugger you will need monodevelop-debugger-mdb. You will probably also want monodevelop-versioncontrolto support SVN, mono-xsp2to run ASP.NET applications, and monodoc-browserto view documents.
Perhaps your best bet is simply to install all the packages "offered" in the MonoDevelop package. I believe that Ubuntu's package manager can easily do this from its GUI.
Beware that Ubuntu breaks Mono into many small packages, so if something is missing, use a tool apt-fileor similar to find the package you need to install.
Ubuntu Mono 2.4; 100% , openSUSE. 2.4 Ubuntu - - , Mono- .