What is everyone doing to tighten up their stomach?

Specifically for stomach, there are some core specific exercises I do at cross fit 2 x a week, core workout 2x a week using roller with DVD trainer. Planks, pushup, Romanian dead lifts, ght sit ups are all examples of good core exercises. Mark answered a similar question yesterday with a list of good core foundation exercises. There are 100s of basic moves and uncountable variations. Yoga is also super for strengthening core if you are into that. I do so many different pushup and plank variations daily to help with core strength.

Adding to Fiddleman's list: V-ups, Superman's, throw downs, weighted ball throw, leg lifts, suicide 2x4 or towel, (land), crunch, side obliques, reverse crunches (I prefer to do these in water for added resistance) with Hydrotone equipment. Good luck...do tell what your favorite exercises will be.