As said the bench press is a good un. Also try and do about 100+ varying crunches at the end of any exercise routine. My spare tyre has improved a great deal whilst sticking to this rule. Vary your crunches as well, i.e. lay flat on your back with legs bent at the knees for 25, then lay your legs flat facing left and do another 25, then lay your legs right - another 25 and finally lay your legs totally flat and do another 25.

Your stomach should be killing you at the end of this - but if it hurts it's doing what it's meant to. Remember that a crunch is not a sit up. Lay your head on the ground and put your hands behind your ears (as if you are supporting your whole head by the tips of your ears) then raise your torso and head by about ten/twelve inches so that your torso is at about 45 degrees then let yourself down sloooowly - without touching the ground repeat. It's tough but it's the only proactive way to get rid of that stomach.

Keep at it!

P.S. awesome respect for losing that much weight, man!