The key to having a good vacation is not always that it is well planned.  However, getting a good deal where ever you go makes for just that much extra cash to just a few extra things.  I also have just started taking vacations by finding the best deal and going there.  Just recently we had a great deal from Monterrey to Vegas but ended up taking a week in Cancun instead with three days on a 45' motor yacht (photos here).

Here are the sites that I use or have been advised to use by people who really know like Clark Howard.

Travel out of USA

TravelZoo.com

AirGorilla.com

Kayak.com

Mobissimo.com

Travel out of Mexico

VivaAerobus.com

Cruises

Cruises.com