I found out about Clif Bar's 2 Mile Challenge about 6 or 8 months ago. The idea is to use a bike for many of those trips from your home or office that are just 2 miles away. The site goes into more detail, but makes a good point about reducing pollution and getting out on a bike more often.
I use the site to map stores, restaurants and other places like the library. My work commute is around 4 miles so I use the map more as a reference depending on whether I am going from my residence or from work. It's been very helpful.
Clif Bar is also visiting different cities to keep the 2 Mile Challenge ball rolling. Pretty cool stuff. It is amazing the difference we can make by just riding a bike a couple of miles to get lunch or do a little mid-week grocery shopping.
To take the challenge use the link above to visit the site and go through the steps. Have some fun!
Day 4, by the way, and another 8.5 miles.