Uprocking/Rocking: The dance itself is something that originated from the New York gangster culture during the 60s. The moves in it are of a fighting style. It's down to the ground and hard-core, so many people that don't know much about it critisize it for supposed "lack of respect". They supposed to be fighting each other, so uprocking is a better alternative. Mainly danced to 60s rock and funk.
B-boying: Something that started making it big in the 70s but actually started in the late 60s. It takes elements from a lot of things but with "bboy" flavor, and is danced to funk and early hip hop. Foundation like toprock, footwork, freezes are really important, but mainstream performers prefer the elements of power and acrobatics. Personally, I think there's better "power moves" at the Olympics; I personally prefer style because it's closer to dancing and gives you a sense of high that you can't get from drugs. ( I don't take drugs haha)
Housing: This is really similar to toprock, except the music it uses has an electronic element. It takes stuff from Jazz, African, Salsa, Tap Dancing, Ballet, Wacking. I really respect this dance because it's old school and funky, but also has new elements. The movements are also alot more difficult.
Popping: Came at about the same time as bboying. It has a pop element followed by the stiff contraction of the body to the beat. Most people that pop nowadays pop to rap and R&B, but the proper music is funk, not "gangster rap".
Locking: This is danced to funk, but modern dancers tend dance to R&B and rap. I'm not a big fan of all that gangster stuff. Locking has origins in the 60s, and its a dance with special wrist rolling and halts and stuff. Not to be mixed up with popping seriously.
Krumping : I've seen some cool things done in krumping, but I'd rather not mess with it. Krumping is a really new style that's like an amalgam of previous dance styles. It's also one of the only dances where you're meant to dance to modern rap and hip hop. People tend to call it "real dancing" because it's emotional, aggressive, and spiritual.
Liquid dancing and raving: Techno and Glowsticks, and spinning them around. Looks pretty cool and I think it's probably pretty hard as well.