Can anyone tell me the name and web address of the website that auctions off last minute flights around the US etc? I used it 7 years ago but have forgotten it.

Otherwise, does anyone have any tips on the cheapest way to get internal flights? I'm coming from Australia next Christmas (when I expect flights will be very expensive!), and want to get from Vancouver-LA-Houstan or Dallas- Cancun-Vancouver over a 4 week period.

Is there any sites that compare all airlines? When do you think the best time to book is? I'm afraid to book with Australian travel agents as I'm sure they won't be the most competitively priced.

Thanks in advance for all your help!

I like to use www.kayak.com for comparison shopping, but I always book directly with the airline from their website. I think it's a little too early to book flights for next December. If you are only flying Vancouver-LA-Houston then I wouldn't worry a bit about flights & prices as you'll have plenty of options. Cancun will have fewer options and since it's a vacation destination likely higher prices at holiday travel time.

Kayak doesn't show all airlines - I think Southwest doesn't show up there so you'd have to go to their website, but I could be mistaken.

I agree, I use kayak too. It does compare prices and also shows graphs of highs and lows on fares. If you are flying over the Christmas holidays, yes, it could be expensive.
I would certainly start checking on fares now to get a feel for the prices.

Not aware of a true auction site. How did that work?
Are you thinking of Priceline? I guess you could call it an auction, they use the term "bidding". Before you use it, lean how to best do it at http://biddingfortravel.yuku.com/

Try priceline.com