Hi Jeff,
Your rtl dongle covers a very wide frequency range from below the VHF band up through UHF. For a single, omnidirectional antenna, I would suggest that you try a "Discone" scanner antenna as sold by radio shack #20-043 and by most or all other scanner and ham radio stores. If you want to try making your own directional antennas for specific bands, Google "cheap yagi" and check out the website of Kent Britian, WA5VJB, for designs of homemade wire and wood beam antennas. Either way, you will need an adapter for the little MCX antenna connector on the rtl. Nooelec sells these.
Greg Ella
Ft. Collins, CO