1. Monoppix
2. Mono Live

Both distributions include mono librarires and tools. Mono Live distribution includes some applications written in mono like beagle or tomboy. Also it includes some known ASP.Net web applications. As a result it is 200Mb more than monoppix.
These cds are live cds meaning that you can boot from them and work on them without the need of a harddisk. As .net developer you will probably use windows and maybe you want to give a try to the opensource alternative. It is difficult to switch to live cds than go back to windows. Instead there is a tool to emulate your processor on windows (on linux as well actually) called qemu. This tool can also work on windows. You can download qemu in windows. You can boot any live cd distribution with this tool.

Simply just edit your .bat file
qemu -L . -m 300 -cdrom ./monoppix.iso
qemu -L . -m 300 -cdrom ./monolive.iso