Well, besides the obvious, like smoothies and such (which taste completely different from regular blenders, texture is THAT important), I make homemade nut butters, mostly cashew since the wife and kids love cashews, but I also like almond butter a lot. I can't even get as good of results with a Cuisinart Food Processor making nut butter as what happens in the BlendTec blender.
You'd be amazed what you can do to make "liquids" for use in recipes. For example, chili. Most people like to use a flavorful liquid, like beef broth or beer, or whatever. I like to toss onions, garlic, dried and fresh peppers and some beef broth for liquid and blend that up. A regular blender at best makes a sauce, it will still have some pieces in it, so it's not really "liquified". With the BlendTec, it is far more liquified and makes for an excellent liquid to use when making chili in my opinon. I do this for many other similar things as well, from soups, stews, sauces, you name it.
You can grind anything up to a fine powder, be it spices, or even whatever crunchy is on hand like pretzels or whatever to make some nice fine breading. If you like, you can turn thinks like iPads and other crazy stuff to a powder. Check out the videos online by searching YouTube with the term "It Blends". Funny farking stuff, and they really did blend all that stuff up in a BlendTec.
Whipped cream, mayo, hummus, fark...the list goes on and on.