first, farecast.com has fare price predictions, suggesting when to buy tickets (1 month before, 1 week before, etc). I have personally found that either Southwests.com or United.com get me the cheapest tickets (although I have not tried calling southwest, but united tends to be more expensive on the phone than online).
For hotels, I would try bidding on hotel rooms (I believe several sites offer this). My grandparents and I recently stayed in a 3.5 star hotel for $75 (total) a night in downtown DC.
Finally, if you want really cheap, try hostels, although sometimes there are age restrictions and curfews, so be careful with that.
For Extremely cheap, try couchsurfing.com, where you go stay in some random person's place (though I like this because they will be local, often have time for you, and know what is fun in the area that most touristy types don't get to do). This is in the states and international, but typically takes some advanced planning as well.
for rental cars, clark howard was mentioning a way to get cars for a few dollars a day, but is dependent on where you rent them and then take them to (as an alternative to flying). The rental car companies use you to transport cars to high demand areas.
ClarkHoward.com usually has decent tips and tricks on traveling, so I would look that up to!
good luck!