While I'm at work I usually use jEdit.
(I'm currently using it for some vbscript (blech!) stuff at the moment).

Syntax highlighting for most languages is handy and the irony of using a java-based program to wrire .net stuff will hopefully make you feel better.

Like Fargus says you don't need an MS IDE (or any IDE) to create .net software.
You can use your editor of choice and create a macro to call the .net compiler.

I highly recommend jEdit though not quite as "big" as Eclipse or netbeans and very simple to use.