After a very long time, I did a new debugger release today. It's more or less a snapshot release and comes without the GUI.
http://primates.ximian.com/~martin/debugger/mono-debugger-0.5.tar.gz
There are also some experimental binaries available for SuSE 8.2:
http://primates.ximian.com/~martin/debugger/mono-debugger-0.5-1.i386.rpm
http://primates.ximian.com/~martin/debugger/mono-debugger-0.5-1.src.rpm
Update: If you're on Red Hat, you need to set the LD_ASSUME_KERNEL environment variable to 2.4.1 (export LD_ASSUME_KERNEL=2.4.1) before starting the debugger.