I've found that I can maximize saving gas and saving money best by carpooling. In March of 2010, I placed an ad on craigslist under the "rideshare" directory and waited to see what kind of scariness would follow. I sort of expected to get spam and nothing else in response, but the response I got was overwhelming. Because I had so many people contact me, I was able to pick and choose the two people I thought might be the most reliable and who had work hours similar to mine.
Long story short, the three of us are all still carpooling together and it has been amazing. Both women who ride with me work for other employers, but they are near my office. They both meet me at my house in the morning and I do all of the driving (being a conscientious hypermiler with an economical car), dropping them off where they work and picking them up again at the end of the day. Carpooling adds an additional 10-15 minutes to my commute each way, which is very acceptable to me.
My fuel economy took a hit when I started doing this, but not too badly. My average right now is 28.3 mpg. Multiply that times 3 people = 84.98 mpg.
And the best part? They split the cost of each tank of gas between them 50/50.
