I am a staunch vi user myself, but can't quite manage to call it an IDE, it kind of lacks the Integrated part. but that might depend on what you want for integration. There are some nice plugins for CVS and DB develeopment, and even ones that claim some IDE capabilities such as project grouping and buffer display lists.
. It's a python app but allows you to choose between several editors including vi.
Of course if you don't use vi, none of this probably matters to you.