If you don't have the strength to do a chin-up, are those assisted chin-up machines (I guess they have kind of a counterweight that you can adjust) at the gym the next best thing?

There are various ways of improving vertical pulling strength.

Those machines will certainly get you stronger. Simply progressively deload the weight over time so you're handling more and more of your body weight.

I prefer a multi-faceted attack and it will depend on the individual.

In general though I like to build the foundation of pulling strength using cable pulldowns and I'll typically throw in assisted pullups with bands and eccentric pullups, too.

I have been able to increase my uppper body strength and arm and shoulder definition immensely using the machine to do pull-ups, chin-ups and dips.

I do the weight assisted pullups.... and i will tell you that i am gradually using less and less weight assistance... and thats all the while losing weight too.... so def has helped me improve my strength in my arms!

It seems like a pretty good idea in concept. I'd love to work up to actually being able to do some regular pull-ups.

As your strength increases and your weight decreases, the possibility will become a reality before you know it.

I mounted a pull-up bar to the floor joists in my basement. Being not strong wnough as I once was to crank them out, I use a chair to assist me. I make sure that I am doing them with my back and my foot is there only to assist.

I great a great work out this way. Doing it assisted also helps in doing them slowly.

Yea, a chair works well. That's what they suggest on p90x. It could be a little unsafe IMO but it does work. Provides essentially the same "assistance" as bands or the machine.