You probably know the no-no is sharp objects (knives, etc.) and liquids. All liquids have to be in a quart zip-lock (per passenger). They don't seem to strictly enforce the 3 oz. rule but I wouldn't push to far above that. I doubt "dry" snacks are a problem. Also, remember you have to take the ziplock bag out at security, so don't bury it in the bottom of a carry-on suitcase. I'm pretty sure you can bring on drinks like bottled water that you bought inside security. If you bring medicines that will be above the oz. limit, have them in the original prescription container (or the prescription box it came in). Of course, make sure carry-ons meet the size requirement (check airline website) Most airlines give you one carry-on and one small bag.
The best place to check for what's okay is
TSA | Transportation Security Administration | U.S. Department of Homeland Security.