Hi there, and thanks for your question!
You are allowed one quart sized bag per person.
Each item you put in the quart sized bag must be 3.4 ounces or less. You only have to put your liquids, aerosols, and gels into the bag.
However, you can fit as many items as possible into your bag -- there is no limit on the number of items -- but trust me, the bag isn't very big :)
This excludes liquid medication -- which you can have more of, and doesn't have to be in the quart bag -- if you declare it when you get to the checkpoint.
Just as a hint, I'd recommend taking an *empty* water bottle with you, and filling it up *after* you go through security. That'll be much cheaper than buying one at the airport.
Reference: http://www.tsa.gov/311/, my own travels
Let me know if you have any questions, and if you're set, thanks for pressing "Accept".