When deciding on the type of bike to buy,
think about these questions:
What kind of riding do you want to do?
Do you see yourself growing as a rider?
What do your friends ride?
What have you had in the past that you've liked?
What have you had in the past that you've disliked?
How much are you comfortable spending?
If you are buying a bike to ride with a group of friends, you are best off buying something similar to what they ride. You will not be able to keep up with a road bike if you are on a mountian bike or a cruiser. And a road bike will not venture into the dirt or sand.
If you enjoyed a three speed as a child, you may find cruisers to be a fun bike again. If you dislike the road bike you bought a few years ago, perhaps a moutain bike or hybrid would be a better choice now.
BMX (Free style or Race) - Specialized, Haro
Town/Cruiser - Speicalized, Jamis, Electra
Youth - Speicalized, Jamis
Mountain - Specialized, Jamis, Santa Cruz
Road - Specialized, Jamis