do a google search - farm machinery books

All of my Agricultural Machine design books are at home.

You could go to www.asabe.org and look around on there.  All of the books will be available through them.  They have a recomended list of books for the PE exam in their PE exam review book.

These are two books I have on my shelf.  I believe there are new editions available for each.

Tractors and Their Power Units, 4th Ed., Liljedahl, et al, ASAE

Engine & Tractor Power, by C.F. Goering, 3rd Edition

First off - anything behind a tractor is generically called an implement.

As for implements, the technology had advanced very little until ~10 years ago when GPS starting coming into the picture. Now you can find GPS enabled variable rate drives, on the go yield monitors, radar speed sensors, etc.

As for combines they to have not advanced all that radically either except for the advent of hydrostatic drives, rubber tracks, computer control, and the aforementioned GPS. Of course there is always the horsepower wars. :)

Tractor technology has advanced quite a bit in the last 10 years. This includes rubber tracks, infinitely variable transmissions (not pure hydrostatic), GPS, NVH control, engine computer control (torque bulge and fuel economy), computer controlled transmissions, etc. JCB has had a 4 wheel fully independant suspended tractor with disc brakes for some time.

I would also suggest going through Ag magazines. The large manufactures like to show off their latest innovations. Cheers.