If you've just recently purchased and activated a new T-Mobile BlackBerry device, then you should be aware about the $50 promotion that's going on with their trade-in program. It works on BlackBerries that were purchased online or at any retail location. Once you got that, just follow this link
and use the promo code “fliptoablackberry” to get access to the site. You'll have to fill in some information about your old phone that you'll be giving up, but just about any phone will guarantee you a minimum of $50. We tried it out and found that a Motorola RAZR will get you $50 while an HTC Tilt will go for $75. It looks like some devices make out more than others, so just be mindful about whether or not its worth the value they're offering. Once you got all that situated, you just have to ship out the old phone, attach copy of the UPC from your BlackBerry phone, and a copy of your purchase receipt. This special promotion is running until November 18, so make sure you get it done before that deadline.