I'd probably keep an eye on eStarland.com. They just had a sale price of $32.95 for one with about $4 or so in shipping. So that's about $15 off MSRP of $54.99.
The only other thing I could think of is one of those game/controller bundles, especially one where the game has some decent trade in value left to it. Case in point: The Uncharted 1/2 bundles with the blue Dual Shock 3.
The Uncharted games from that bundle can be traded into Best Buy with their current 100% trade value bonus for $22($23.10 if you have their Gamers' Club Unlocked), thus netting you a controller for around $37 after trade because the bundle is $59.99 normally.