What am I talking about?
Well, honestly, lots of things...
one of the more well-known of course, is the build-your-own shoe page on Nike's website. Here you can select a basic shoe style and dictate everything from which Nike symbol appears on the tongue, to what colour the airpocket in the sole is. And at a price fairly similar to what you'd pay in stores.
You can also design your own ring on the 'A Diamond is Forever' site.
While slightly different, but, with the same 'power to the end-user' spirit, Home Depot is tied in with a software called Big Hammer to design things like sheds.
Or you can design with legos! You use the software, upload your design and order your model from them.
You can custom make men's and women's swiss watches at 121time.
Well, forget buying things... just create your own items through cafepress and sell them to others.
You can even generate your own comic strip using online resources.
Another fun one is creating simple word search puzzles on Superkids.com.
Of course, there is also eMachineShop, where you can design your own part and have it manufactured and shipped to you!
or you can select models for your pneumatic system on SMCworld to help you design.
So, for us do-it-yourself'ers, we don't have to stop with hanging shingles... we can just fire up our internet browsers and build the world.