A while back, I wrote a guide to the first truly professional and practical DSLR camera, the Nikon D1, titled: Photography: Going Pro for $200: Revisiting the Nikon D1.
That volume proved popular and I hope it helped some photographers to get started with their first pro DSLRs. The aged D1 may not have the megapixels of modern cameras, and it certainly has some frustrating menu items, but it is a fun and inexpensive way to get your hands on a pro DSLR without spending a lot of money.
This book recently was expanded for print and adds details about the Nikon D1x and D1H.
The thing is that, if you are like me, once you've shot with a pro DSLR, it makes you hungry for more. But those current models - the Canon EOS 1Dx and Nikon D4s (the latest as of this writing) - still have huge price tags that can bring tears.
The best thing is that, used, you can put your hands on a D2x for less than $400 and get one of the best lenses Nikon makes - the Nikon AF D 50mm f/1.8 - for another $100.