Several readers have pointed us towards the listing for StarCraft II on GameStop's website, where preorders now snag you an invite to the eagerly anticipated strategy game's beta test, as long as you agree not to cancel your order afterwards.
There are actually three ways to obtain a StarCraft II beta code through GameStop. You can preorder StarCraft II: Wings of Liberty online and receive your code through email; preorder the game for in-store pick-up, wait 24 hours, and then go to the store for your code; or preorder the game at the store itself, with the code printed out on your receipt.
If you choose either of the first two options, however, make sure you really want to purchase the full game, for there is a disclaimer:
Reserve StarCraft II: Wings of Liberty and receive an invitation to the StarCraft II: Wings of Liberty beta. Available online and in-store while supplies last. Once you receive your Beta Code your order cannot be canceled.
Your best bet is to head over to your local store and drop five dollars on the game. You'll get the beta code, and should you not find the game to your liking, my local GameStop manager says that retail stores will still allow you to cancel your order after the fact.
Thanks to everyone who sent in this tip!