I bought a copy of MOJO (Paul McCartney interview featured) as I usually do, for about £3 I think it was (again, normal newsagent price).
Read it, and put it up on Ebay. Guy in NZ bought it for £10 when if he'd waited a month he coulda bought it there for at least 1/3 of that (No idea how much MOJO is downunder... I think about $7? Anyone?).
There's definitely money to be made - thousands of people run auctions on Ebay as their fulltime job (and make enough to survive and more!). I plan to start going to local auctions and buy nice, cheap shit and then selling it online. Just small to start with, obviously... I had planned on hitting charity shops, too, but they're pretty canny these days and charge through the roof for some things.