You can easily flip items by buying them cheap on RMAH (cuz people sometimes just want some $$$) and sell them for more on Gold AH..
I think in 1 week i bought 15 witching hours for 1.50-2 euro each by bidding and then i sold them for 15-25 mil, so i basicly got a profit of 5-6 euro easily. Though it's not alot of money it's still something just for pressing 2 buttons and using 2 minutes of looking through AH.