I’ve been a huge fan of projected textures ever since they put them into Firestorm. Not only as a photographer, but as a builder as well, you can get some pretty amazing results.
The short version is: On any given prim, on the Features tab, there is now a second box next to the color picker for the lightsource coming off of the prim. You can project a texture. VERY simple applications like spotlights are made easy with this.
But I’m not gonna go through and explain it all- Torley’s already done it in his bouncy, fabulous way. Check it out. You can do some really amazing effects in world with this.