I often use Eclipse when I develop Java-based software applications. Installing Eclipse on FC4 is easy! I don't normally do development on Eclipse itself, so I install everything except the *-devel packages:
$ sudo yum install `yum info eclipse\* | grep Name | cut -d: -f2 | grep -v devel`
Surprisingly, this installs 70 packages!
To run Eclipse, I select Applications/Programming/Eclipse. This Eclipse has an unusual splash screen, announcing itself as
Based on Eclipse 3.1.1
I haven't done much with it yet, but it looks right so far.