Don't waste your time with any of the garbage/overpriced antennas at Radio Shack or Wal-Mart.
You really need to do your shopping online. Even with shipping, you can find a quality antenna for around ~$100.
Based on your zip code, you're in one of those rural OTA blackholes. Very few channels will come in via digital with any old cheap/sub-standard antenna. As other posters said, you need something directional, and quite large.
The amplified setups you'd find at Radio Shack are fairly useless with the mileage you are from the TV stations you're looking to pick up.
Personally, I can recommend a Channel Master 4228HD. I recently got it and have it hooked up to my Zenith DTT901 converter box. I'm in Hudson, NH (03051), and my location has trees all over the place (it will be interesting to see how reception is once the trees fill out with leaves). Channel Master and Winegard make excellent quality, high performing antennas for receiving OTA TV signals. Depending on what channels you are trying to pick up a high-gain UHF or VHF only antenna and preamp may be needed for your situation.
While a certain antenna may be a great performer, there is no one antenna that works best for everyone.
I get all of the Boston stations at around 90% signal strength, and even WMUR (Ch 9) at around 75% signal strength, which is in the opposite direction that the antenna's facing.
Some good online stores for antennas are:
http://www.dennysantennaservice.com/
http://www.starkelectronic.com/
http://www.solidsignal.com/
http://www.summitsource.com/
http://www.antennasdirect.com/ (Sells their own brand only)
Some good sites for antenna info
http://www.hdtvantennalabs.com/index.php (Antenna reviews)
http://tvfool.com/ (Another DTV checker like Antennaweb)
http://www.avsforum.com/avs-vb/ (Great forums for antenna and converter box info/reviews/help)
There may be a large up-front cost for a quality antenna/preamp, but it's a one-time thing. It will last you for decades (if inside or protected). With cable TV service, you are paying continually, on a monthy basis...