While I don’t like rap, I do like a few rap songs and groups because they are actually pretty catchy tunes.
I would have to say it is between Cypress Hill’s “Insane in the Membrane”, Tone Loc’s “Wild Thing” or my new favorite (that I love to hear when I am working out) House of Pain’s “Jump Around”. Just even having that tune in my makes me start bobbing(I guess that is the right term) my head around. 
Well what are your picks or do you agree mine are the best. 
The Message Grandmaster Flash and the Furious Five.
White Lines - Grandmaster Flash & Melly Mel
Any song on A Tribe Called Quest’s “Low End Theory”
I enjoy anything by Run DMC, especially “Mary, Mary” (not just because it samples the Monkees)
Also, The Beastie Boys, “Paul Revere’s Ride”
Public Enemy, particularly “Bring the Noise,” but anything off of It Takes a Nation of Millions to Hold Us Back.
I think Sabotage by the Beastie Boys might be stretching the genre a little, but Can I Kick It by A Tribe Called Quest, Bug Powder Dust by Bomb The Bass & others and Nouveau Western by MC Solaar would be my top three.
I don’t think I’m qualified to hazard a guess regarding the best of all time, but currently there are four which I consider to be at the top:
DMX
Busta Rhymes
Cypress Hill
OutKast
If you saw OutKast on Letterman last night, you would have to agree.
Almost anything off Public Enemy’s “Apocalypse 91: the Enemy Strikes Black”
I LOVE Public Enemy, although as a white girl I feel a little self-conscious blasting it while driving around (kind of puts me in the mind of “Pretty Fly (for a White Guy)” by the Offspring) 
Still, Chuck D rules. If you’re going to listen to rap, listen to Public Enemy.
I’ll second most anything off PE’s Nation of Millions…, add Run DMC’s Peter Piper, Lotsa Tribe Called Quest, LL Cool J’s Rock the Bells, Eric B & Rakim’s Paid In Full (and Don’t Sweat The Technique), Slick Rick’s Children’s Story, …
Best rap song - Eric B. is President, by Eric B. and Rakim
Best rap group - Wu-Tang Clan (if you include member’s solo albums as Wu-Tang albums, most people do.)
Best rap album - Enter the Wu-Tang
Most underrated rapper/group: Kool Keith, and anything by Ultramagnetic MC’s or Dr. Octagon
Best individual rapper (MC) - impossible to say, here’s a few: Q-Tip, Method Man, Snoop Dogg, Rakim, GZA
Most overrated MC - Eminem, he is more of a novelty than anything.
Best producer: either the RZA or Dr. Dre
Again, Public Enemy. It Takes A Nation Of Millions is widely considered one of the most important rap records of all time.
Check out allmusic.com’s review of it here: http://allmusic.com/cg/x.dll?p=amg&sql=A28187 where it begins “Arguably the best hip-hop album ever made…”
It was particularly significant at the time becuse it was one of the first hip hop albums concerned more with pride and responsibility than material possesions, IE: Run DMC.
This is the album that first enlightened my little white boy self to a culture otherwise foriegn to me.
It’s a brilliant album, but not imediately accessable or catchy as “Jump Around”, if that’s more what you’re looking for.
Easy, I’ll go with the first really influential rap song, which is “The Message” by Grandmaster Flash and the Furious Five. The lyrics are even more relevant today then when it came out around tewenty (!) years ago.
Keith
Listen to “Fallin’” on the Judgement Night soundtrack. Its a collaboration between De La Soul and Teenage Fanclub. Great song, even if you don’t really like rap.
“Bust a Move” by Young M.C. … ok im tripping… but really id have to say “Juicy” by the Notorious BIG
I have to agree with all the others who said “It Takes a Nation of Millions to Hold Us Back” by Public Enemy as the best rap album. It’s amazing.
My favorite song off that album is “Night Of The Living Baseheads”.
My favorite rap song is “It takes two” by Rob Bass and DJ EZ Rock. It is very catchy and fun to listen to.I agree with you about “Jump Around”.
Chicken Huntin’ - ICP (hell yea’ I’m down wit da’ clown!)
Still Not a Playa’ - Big Pun
C.R.E.A.M. - Wu-Tang Clan
Rumpshakker - Wreckxn’Effect
and
Best Group… hmmmmm… NWA probably…
I agree with your first line. I dont’t even like rap.
The most I’ve ever heard is the 30 seconds worth waiting at the light when some loser has the bass turned to Stun.
Best group: Public Enemy
Best Song: “The Message” by Grandmaster Flash