The most boring commentary I've ever heard was the Farelli's "Me, Myself & Irene"... it basically consists of nothing more than "That guy in the background ist my uncle... and that girl left of that building is my sister's ex college-roomate... oh, and that couple on the right is my brother-in-law and my wife..." I GOT IT!
Really funny commentaries are made by Trey Parker and Matt Stone (the "Orgazmo" one is just classic... the booze-level rises with each minute of the film). Funny: Bruce Campbell's "Evil Dead 2" bashing in his commentary... I still have to listen to his "King"-commentary on Bubba Ho-Tep.
Funny AND damn interesting: All commentaries by Kevin Smith... and basically most interviews and articles he does...