A friend of mine did the 200 Sit-Ups program this year and was able to do 200 consecutive sit-ups at the end of 6 weeks. They have a free pocket guide and a $3 iphone app to help you log your progress and handle the timing (lucky me, I have a crappy blackberry, but an egg timer would work also).
They also have a program to do 100 consecutive push-ups, but I'm not even thinking about it since I have NO arm strength!
I'm starting this week. Has anyone done this program?