I forgot to mention that you can also get your airlines tickets from Hotwire. Sometimes, you can get lower fares through them, though, not all the time. I usually double-check with my favorite airlines after I look at other sources.
To verify which airlines are offering lower air fares, check out the website:
INTERNET AIR FARES They are 99% accurate as to what the cheapest available air fare may be available. The 1% error may be due to the time lag between programs being sold out and their ability to update. You do not have to book through this agency, but you can. Personally, I find it more of a hassle booking through them than going to the airline company directly.