Even most mortgages with a prepay penalty DO allow a certain fixed amount annually of prepayement - I believe I've usually seen 20%. You can read your mortgage to see what is allowed.
In either case, one can easilly accelerate the mortgage on your own, by sending no more than the allowable prepayable, to be applied toward principal, with any payment they wish. I pay something extra every month with my mortgage, anywhere from $15 to $200 each month, as available. Each monthly statement gives the new balance.
What's great about this is that, if you have an ARM (I have a portfolio ARM which is now 4.875, 8 years old) It has a max adjust of 1% up or down annually. Anyway, the PAYMENT adjusts each year based on the remaining balace and the new rate, so the more I pay, the lower the balance the next adjustment is based upon.