mono is in repo now, tough there is still a problem similar to python, copying /tmp/tcloop/mono/usr/local/bin/mono to filesystem is a temporary fix (or simply use cp2fs flag), i will add a tce.installed script to do that later.
most important thing to note about compiling mono on tinycore is that mono by default uses relative paths which causes problems because mono searches .dlls in mounted location instead of /usr/local/lib/mono
other mono packages which are not necessary for end-users but useful for developers
monodevelop (depends on gnome)
so far i have trouble compiling nunit,nant
why i did this because i believe mono is a milestone for many applications such as open office, f-spot, tomboy notes ...