Bicycle commuted 219 / 220 days. But my commute is a 4 mile r/t, so my total mileage from commuting was only 876. I didn't track other non-recreation miles, but it's not much because I live a mile from the store -- so I'll just stick with the work commute.

876 miles / 20 mpg = 43.8 gallons

In terms of dollars, I get $2 / day from our county rideshare program. I saved $40 / month on car insurance when I updated my policy (a couple of years ago) and told them that I don't drive daily. Not sure about maintenance that I saved, since I didn't actually do any automotive maintenance in 2007 -- I drove my car less than 1,000 miles. We use the wife's car when we go out in the car, mostly. So my rock bottom total savings:

$2 / day * 219 days = $438
$40 / month * 12 months = $480
43.8 gallons * 3.10 / gallon = $136

Total: $1054