If you're thinking about Grapple, I'm unaware of a feat that allows an attack after a successful grapple, although the normal grapple rules allow you to grapple, then use an iterative attack to deal damage.
Improved Trip allows you to make an attack after a successfull trip check.
Improved Grab isn't a feat, but a monster ability that does the reverse - a successful attack lets you automatically take a grapple check (after dealing damage).
