I'm serious considering buying a small motorcycle. Something with a 250cc engine would have decent power, and would get at least 60 mpg, which would be perfect for all my usual small trips.
Apartment to campus = 1 mile
Apartment to home = 15 miles
Home to girlfriend's place = 12 miles
Apartment to summer job = 4 miles
That really adds up over the course of a week in the car. Taking estimated statistics I've compiled from the past year, I will have spent $1350 in gas by the middle of May, at which time I will have owned my car for one year and driven it about 13k miles. The numbers I used were an average of 25 mpg for the Contour, and an average cost for the past year of $2.60 per gallon for premium fuel.
I estimate that if I got a bike, I would drive the car 8k miles and the bike 5k miles per year. Using my earlier figures, that would amount to a little over $1000. That's assuming the bike gets 60 mpg, which is a conservative estimate since the bikes I've looked at so far range from 60-80 mpg. That's also assuming that gas prices stay the same. As gas prices increase, the differential of over $300 per year would only increase.
My budget for a bike is $1000 to $1500. For that price, I can get a small bike, only a few years old, and with only a few thousand miles. Assuming that my assumptions stay true over the couse of the next 3-4 years, that's how long it would take for the bike to pay for itself.
Of course, that's not considering the cost of maintenance or insurance. However, the cost of insuring a motorcycle is usually very little, especially a small cheap one like I would be buying, and I wouldn't expect the total maintenance cost of the car and bike to be much more. I'm going to wait until this summer when I have the money, and make my decision then. Likely the choice will be between either putting a full new dual exhaust on the Contour, including headers, or buying a bike. Hmm.
! Well that and drive my Jetta more 
. The CSVT hibernates most of the time anyways , so it's no real biggie . With the weather getting pretty nice , I'll be getting into my road-biking mode , so less time to gas-azz around too . To bad it's not really feasable to ride my bike to work (since I moved further from work a few years ago) or I'd be ALL over that , no doubt . I also plan on riding the SR500 to work quite a bit 