I don't know if it works with .Net stuff -As .Net is Microsoft's- but Eclipse will work with Java and C++
( There are tons of language plug-ins for Eclipse )
I have used Mono and it is OK. The problem I ran into is that for some things, the APIs implemented for .net and mono were different. I recall running into this when doing database access. You couldn't get me to program in VB with IronPython available.
Honestly, if you have to program in vb.net and ASP, you are best sticking with Visual Studio.