Josep sent me a link to this great tutorial on PSDtuts.com by Jeremy Roux. It teaches you step by step how to create your own Photoshop mockup of a BlackBerry Bold. You can obviously extend this and start making your own mockups of the BlackBerry Thunder/Javelin/Air/Inspiration or whatever codename you wish to make up.
So if you were wondering how BoyGenius and the other myriads of fans create their own mockups check out the directions. Keep in mind you will need to have a copy of Photoshop handy. You might be able to get away with the free GIMP but your going to have to cut some corners and figure it out by yourself.