I have been using resistance bands for pull up. http://www.ironwoodyfitness.com/fitness-bands.php. Scroll down the page for the assisted pull up package. I bought a full set of the bands as they are great for doing a variety of other excercises that integrate well once you get beyond the basics of the pull up, push up and squats of this system.
I also have this pull up bar system, http://www.tacticalathlete.com/tapsbar.htm. It is expensive, but if you can afford it, well worth the money.
Me male, 47, 220 lbs, 5'10". Former paid firefighter/EMT. My goal is to lose 40lbs. and be stronger now than when I was in my twenties. This is the best place to start that I've found, and I've been looking.
There is more great info at http://www.crossfit.com/. There is a great forum over there with good info once you get beyond the basics. Good luck to all newbies, like me, who are starting out.
And again, many thanks to the admin (I think your name is Kevin) for putting this site together. If your looking for help moderating the site, please let me know.