I know this is an old message thread, but I'll reply anyway, as I know not everyone can easily do pullups.
I bought a cheap pullup bar from Wallyworld and installed it in a doorway. I have a routine where everytime I go upstairs in my house, I will automatically go over to the pullup bar. Initially I couldn't pull myself up, and I mostly hung from the bar. I then started adding exercises like legs lifts while hanging. As my muscles have slowly been building up, I'm finding that I able to finally do one pullup. I know if I keep at it, they will slowly increase. Persistence is the key. I feel pretty weak only being able to do one right now, but it's one more than I was able to do 2 weeks ago.