It looks like WireFly and the Discover BlackBerry website have a promotion going on where you get a $100 gift certificate for BlackBerry accessories for buying a BlackBerry online. Most of the the current BlackBerry models qualify for this offer with one notable exception. The BlackBerry 7130e, my personal favorite, is curiously missing from the line-up.
Some of the available models are free after mail-in rebates that you get for signing up to a service agreement with the respective service carrier.
$100 bucks will pretty much get you most any BlackBerry accessory that you want less maybe a Swarovski Crystal encrusted BlackBerry case. You should however, be able to get most other accessories such as “regular people” BlackBerry case, extended battery, or Bluetooth headset. etc.