ASP.NET 2.0 Master Pages
Master Pages are good way to create controlled templates for sites. I use them personally to create a couple forced interfaces and thus organize all of our interfaces in a couple of files. Good things is that if you wanted to change something, you would only have to change one file to affect the whole site. With this new plan of attack, designers and developers can now work together to make a common interface without stepping on each other toes.