I dunno what your "definition" of hip hop is, but here are some of my recommendations that I've came across as putting live back into my hip hop from the typical usuals of mine like Mobb Deep, Wu-Tang, Roots, your typical breakbeats and remixed Jazz, etc..
Lyrically/Rap wise:
Akinyele
Arrested Development
Dr. Octagon
The BeatNuts
Joe Budden
Actually the last one I've recently rediscovered him. I thought he was a one hit wonder with "Pump It Up", and never paid much attention to him, but a buddy had a mix CD and said "listen to this". I was pretty shocked cause he's damn good. Listen to "3 Sides to a Story" and "Roll Call" and some of his other stuff on Mood Muzik 2, it's SICK. He calls out A LOT of people, talking about how hip hop is dead, shiny mouthes, how people thought he fell off, was a one hit wonder, etc. He has no hook, it's just straight rhymin...he's recently been on my play list quite a lot lately.