I've done 2 workout plans in the past that have helped improve my push-up count. I was able to max out the pushups on a mock PFT for the TAMU Corps of Cadets the other day, (74 in 2 min), which I believe is near the max for the CFA for the SA's
1) "The Navy SEALs Workout" on youtube
Dips x 12
1 min pause
Dips x 10 and hold 15 seconds
1 min pause
Dips (faster) x 15 and hold 1 min
1 min pause
Regular push-up (slow) x 10
shake it out
Regular push-up (faster) x 10
shake it out
Tricep push-up (slow) x 7
shake it out
Tricep push-up x 10
shake it out
Regular push-up x 10
shake it out
Tricep push-up (faster) x 7 hold for last two
shake it out
Wide grip push-up x 10
shake it out
Regular push-up x 10
shake it out
Tricep push-up x 10
shake it out
Dive bomber push-up x 7
shake it out
2) The Ray Lewis Deck of Cards workout or "The Prison Workout"
This one is tough and for a person that is more advanced in push-ups.
Go through a deck of 52 cards with 10-60s between each card
Face Cards: x amount of pushups per card (ex. draw a 7, do 7 pushups)
Jacks: 10 pushups
Queens: 15 pushups
Kings: 20 pushups
Aces: 25 pushups
Jokers(optional): 50 pushups
This workout burns BAD, make sure to stretch before and after this one, but it gets easier the more times you do it.
Also, I have a good chest and shoulders weights workout too that supplements the push-ups and made me a lot stronger. It has a lot of bench, incline bench, flys, shoulder press, rope pull downs, and etc.
Take the advice the other posters in this thread gave too. There was some good info in those posts. And make sure your form is good too.