Hit the websites for the airlines that serve your area (esp the "hub" ones).
Also look at the travel sites such as Travelocity, Orbitz, Expedia, yahoo etc. I've been liking
http://www.sidestep.com lately.
In these sites look for stuff like "Vacations", "last Minute Getaways", "Flight+Hotel and Save More" and so on. You may need to poke around in each site as the way they are presented vary.
Most of the sites will even give you an "Need Ideas" area where you can look at criteria such as "Under $250", "Romantic" bla bla.
Usually you can also plug in your airport and match up a city and/or region (NYC or NY Vicinity yield different choices, for ex. You might try Houston which could take you near Galveston, Padre island, Port Aransas, say)
You will be surprised at the good stuff you can come up with!
NB: the deals for Last Minute are often 4-day packages so they mightn't work if you want more time.
Too, sometimes if I see a bunch of stuff for one airline on a Travelocity-type site, I'll check that airline's too since they all offer different stuff.
Frontier seems to have a sale on; lotsa Mexico.
Sign up with all the sites for weekly web only specials.
*Important: check back to these sites OFTEN. Deals come and go all day.*
Lettuce know where you decide to go!