I used to ride and have been considering taking it up again. Motorcycles tended to bring me a constant flow of all the wrong women, but it was still fun. If you ever see a guy and a girl on a bike together, they are fvcking. Even if they have just met, they are about to fvck. All defenses crumble right away.
I had a 90 Suzuki GS500E; it's a sport bike with less fairing.
http://www.devin.com/img/gs500e-black-factory.jpeg
I still see newer bikes in the same style. It was super quick, 0-60 in under 4 sec, but a small cc bike will not have a high top speed. Tops on that Suzuki was about 115-120.
I also had a 1980 Kawasaki LTD1000, a giant bike.
http://www.dragstore.com/uploads/1527.jpg
The guy I got it from had re-bored it to 1087cc and had planned to drag race it.
He was going to make it into this:
http://www.rpcrace.com/images/80ltd.jpg
but he ran out of money.
It was an old bike that did not look very fast, but the owner said it outran every street bike he met, at least on the straightaway. I never opened the throttle all the way, because I felt like I would fall off the back. I'm used to the rear-set pegs of a street bike.
Your body size will in part determine what you should get. I am 6' 170, and a 500-600 cc bike works fine for me. Passengers change everything, though. Sport bikes are not meant for long rides for two, but a not-fat chick still fits on the back.
http://www.r1-forum.com/forums/index.php
http://www.kneedraggers.com/
http://www.motorcyclegearreview.com/
http://www.rapidracer.com/index.html
Wear a helmet and the right safety equipment. The safety course will teach you to look farther down the road as you ride. Look to the horizon, and look through curves. These skills make you a better driver of cars as well.