I usually ride my bike around town. Its the most efficient way to get around, and it's sooooooo much fun.
Look smart as you steer those streets.
The biggest argument about riding you bike is that it's too hot. Not true. Because the bicycle is so efficient, you are using up less energy than walking. With the steady stream of wind in your locks, it is as if mother nature has her AC on.
Go to the market. Go to the library. Go to work. Go throw your seed bombs into empty lots. Go get drunk. Yes, you can also ride your bike to the local pub. It's fun to bike tipsy, I swear. Fun time happy time.
Oh, so you want a bike? Very well. Here are your options:
These bikes are super fancy. They have nice breaks, nice shocks (do you need crazy shocks like these?), super fatty tires with which you can over-run a mole with sharp teeth. If you're commuting around town, this might not be so necessary.
These bikes are a hybrid of the mountain bike and the road bike. This is very suitable for commuting around for the local grocer, etc. They are comfy, have gears for city slopes, and are very practical. The best thing about these is the upright seating position.
These bikes are the ones with the super skinny tires. This bike will zip you to your destination. They are fun, fast, sleek and wonderful. But careful when you see glass on the street. And road bikes are just for roads. No dirt, bumpy terrain, especially no gravel. Stick a rack on the back, and you're set to go. Zoom past cars on the street, smooth riding to the bar. Con: you better know how to fix a flat, you're going to be bent over while you ride.
Little BMX bikes
These bikes look like your 8 year old little brother's bike. They take 50 pedal rotations to move a wheel 3.14 feet. Not so awesome, but your street cred will skyrocket with the 14 year olds down the block.