As far as hip hop/urban. Alot of people in the industry stick to primarily using hardware like mpcs, audio keyboards, groove makers.
If you can get a good keyboard (I'm running a yama portable grand piano) with some descent software, you can put out some pretty cool stuff. Alot of the keyboards come with lots of different instrument/voices to work with, so gives you alot of options.
As far as software: One of the industry standards and is recognized in alot of studios is 'ProTools'. Also, Reason 3.0 is great. One downside of these programs is that they have a pretty large learning curve and definitely aren't easy to pick up on to.
For starting out, Acid Pro is a great program to use and is pretty user friendly. Fruity loops is another program that is good and is even more geared towards techno/trance/electronic if you want to go that route.