Oldest: Paid in Full - Eric B. & Rakim (1987).
Newest: Channel 10 - Capone-N-Noreaga (2009).
Also, what do you think will be your next hip hop album purchase?
I just pre-ordered Eminem's Relapse a couple weeks ago. My next purchase will probably be either Cormega's new upcoming album Born & Raised or Eminem's Relapse 2 (at the end of the year, if it's still released). I would've said Dr. Dre's Detox but who knows when that album will see the day of light.