dunno about Intel, but AMD i know, at least for their Phenom II line...
The 900 line is the full-featured set, with quad-cores and full 6MB of L3 cache, the most expensive, but the best!
(Black Edition: ability to overclock your processor by changing the multiplier only)
Phenom II 955 BE 3.2 Ghz
Phenom II 945 3.0 Ghz
The 800 line is basically quad-cores, with the cache reduced to 4MB, in an effort by AMD to sell processors that don't make the 900 grade.
Phenom II 810 2.6 Ghz
the 700 line is triple cores, since one of the cores were defective and thus disabled. Still has the full 6MB of cache for all cores.
Phenom II 720 2.8 Ghz BE
Phenom II 710 2.6 Ghz