Your abs pretty much get worked all the time doing basic daily movements eg) bending down to pick something up...crunches won't do anything but tone the muscle underneath the fat. You can do 1000's of situps and it won't do anything if you aren't on a good cardio program. Cardio is the only thing that will burn the fat off and away from the area...also you can't spot reduce specific areas. Fat comes off the body where ever the body chooses...usually the stomach is the last to go. It's good to tone up the muscles underneath, but to get rid of the fat in front, you need cardio.
As for flabby arms...incorporate working your triceps & biceps...I've pulled a site for some tricep ideas
http://exercise.about.com/cs/weightl...mpletricep.htm