You can enter the code over at http://www.blizzcon.com/beta and enjoy the satisfaction that you'll get knowing in a few months (or less?) you'll be playing the beta of StarCraft II.
The code took me a few others on staff a couple tries to enter. 'B' looks like '8', and 'S' looks like '8'. You'll probably need to try a few different permutations of the code until you get it right. When you enter the right code, you'll get an email 'confirmation' that really just tells you that you've entered the key successfully. You don't have to do anything further. The email is a little oddly worded though, and doesn't look like your typical Blizzard email. So we've posted a copy of it after the break for folks.
BlizzCon 2009 is coming up on August 21st and 22nd of this year. We'll be there in force again. Should be a blast!