Sorry for the Glen Campbell reference - couldn't resist, I'm getting help with it.
I promised some more on Eric Shupps excellent presentation on Custom Site Definitions. There's a guide on Mr Shupp's blog on how to build a Custom Site Definition. There is also a good diagram of how a Solution Package breaks down.
The Cowboy is also going to put up a VS2008 base solution for a a site definition and I'll pop that link up when I get it