EASy68k is an excellent little IDE for the Motorola 68000 family of CPUs, allowing you to edit, assemble and run 68k assembler programs on Win32. The simulator runs fine on Wine, but the editor has a strange problem of not recognizing newlines which makes it pretty much unusable.
I couldn't find a fix for this odd behaviour and was ready to give up and install Windows in a VM (on a netbook!), but then I noticed the editor doesn't have any problems whatsoever with files written in other editors. This means it can load and assemble files written in e.g. Vim just fine - a good enough solution for small-ish programs required by my class.