Well, woodcutting is always a good money maker if you're patient, due to the massive payout when you hit lvl 60, and the time it takes to increase the stat is relatively low.
Another decent method is grinding at the cows north of the Lumbridge chicken farm, near the glider. You can bank quickly there with the deposit box, and the hides, bones, and beef all sell ok on the GE. You'll get combat exp too.
Mining is also profitable, but very frustrating, as you can have difficulty getting coal on F2p worlds.