I have one of those doorway mounted pullup bars in a main hallway of my house. That hallway connects to the kitchen, livingroom, and is on the way to one of the restrooms. I make it a point to do 5-10 pullups or chinups everytime I pass through so in the course of a day I'll be doing anywhere from 50-100 pullups.
My bar is similar to this one, bought from the "As Seen on TV" store in Ala Moana, bought for about $40:
I like this one because of the various grip options for a varied workout. It's a great piece of equipment because of how easily it can be incorporated into a daily routine. You can" workout", without having to take time out of the day to workout.