Well you have several options available:

1)You could patiently research your local Craigslist in hopes of finding a chromoly steel hybrid/mtb bike from back in the '80's.

2) You could order a hybrid online:
www.bikesdirect.com/products/motobecane/elite_sport.htm

Or a road bike online:
www.bikesdirect.com/products/windsor/wellington1_IX.htm

3) You could order a single speed online and then join a bicycle co-op to build up a hybrid/mtb frame that you get from that very same co-op. You'll end up with two bikes, instead of one. The single speed will take care of your commuting needs. The co-op project will be your trail/recreation bike.
www.nashbar.com/bikes/Product_10053_10052_504148_-1_202339

4) You could just volunteer at a bicycle co-op. Obtain your membership. Share with others about your desire to become a bicyclist, but have no bike. They will then, work with you in terms of building your own bike. You can start with one of their donated frames.

5) You could get a Schwinn Frontier MTB ~ $330 @ a Schwinn LBS
www.schwinnbikes.com/bikes/mountain/2012-frontier-mens-14351

6) You could get a Jamis Trail XR MTB ~ $330 @ a Jamis LBS
www.jamisbikes.com/usa/thebikes/hardtails/trailx/12_trailxr_bk.html

7) You could get a Giant Sedona Chromoly Steel Hybrid ~ $350
www.giant-bicycles.com/en-us/bikes/model/sedona.st/9025/48885/

8) You could get a Giant Cypress Chromoly Steel Hybrid ~ $350
www.giant-bicycles.com/en-us/bikes/model/cypress.st/9019/48871/

- Slim