Well cheltenham starts tomorrow and Victor chandler are offering a £20 free bet if you place a £20 bet on the Supreme Novices Hurdles (obviously  you lay this off at the closest odds you can find at Betfair)
They are also offering 20 free spins on a slots, for placing the initial £20 bet.

Check out the full guide here for details of the Matched Betting technique

At big events like Cheltenham, online bookies often increase their sign up offers for newcomers and also may give free bet offers to current account holders,