As for C #, you really have no choice, MonoDevelop is the way to go, and in my little experience with it, it is good enough (most of my C # work was done in VS2005).
As for C ++, I had success using Netbeans (6.5 + 6.7beta) to edit and create an old obsolete application that uses handmade Make files and many other scary things that you won't find in any recent project on C ++. In our case, there were few hands that needed to be done when setting up (creating a project, then manually adding switching paths and what not), but after that it worked almost flawlessly. Code completion worked just fine even when using different levels of template usage, although in one case it had problems (some automatically generated code from Liquid XML 4).
Java Eclipse - , , Netbeans - , , groovy, php, ruby python, .