Roger Cicala of Lensrentals.com has posted an article describing his disassembly of a Nikon D7000. Amply illustrated with pictures, the post gives a good idea of the internal complexity of a modern DSLR. 

Cicala also recently disassembled a Sony NEX-3 CSC camera, which has a much simpler internal construction, he notes. 

Update, April 13: Cicala has also partially disassembled a Canon EOS 5D Mark III, and he's impressed with several aspects of its internal design and construction.