Back on March 14th Martin Baulig announced the latest release of the Mono Debugger on the Mono-dev list. This release now supports C# 2.0 in a limited form, according to Martin:
The biggest news is that the debugger now has support for C# 2.0 features such as generics, anonymous methods and iterators .... Unfortunately, the debugger doesn't work with the released Mono 1.9 anymore, you need to grab the latest mono from SVN HEAD.
To use the latest debugger with Mono you need to download it from SVN HEAD and recompile both your applications and libraries as the debugger no longer supports the older symbol file format.
In follow-up, Miguel de Icaza promoted a Mono Debugger patch posted by Harald Krapfenbauer to Mono-dev which adds remote debugging capabilities. Miguel also indicated that MonoDevelop 1.1 will have support for the debugger.