What's a good exercise to do that will help get rid of that embarrassing flab that hangs down when you lift your arms up? lol I hate my arms and that's probably the most embarrassing thing about them.

Weight lifting, arm curls and there are some specific under arm muscle exercises as well

is there an online site or something that shows the good underarm muscle exercises? I wish I could afford a personal trainer, but being on my own, any tips are appreciated

You can't spot-burn the fat on your underarms, just not possible. Keep losing the fat, and it will come off with the rest of it. You can build muscle to fill out the skin which will make things look tighter, but I wouldn't recommend just working the tiny triceps. Check out a book like New Rules of Lifting for Women, Body for Life (good online site as well), or the online sites ExRx or stumptuous (dotcom...might have botched the spelling on the last one, but google can probably fix it ) for a full body workout program.

good to know, thanks! and I'll check that out!

Oh that's what I meant- that arm exercises can tone you up- just google something like "arm toning exercises."