Here are some quotes from Freegan.info that I find particularly enjoyable.
By recovering the discards of retailers, offices, schools, homes, hotels, or anywhere by rummaging through their trash bins, dumpsters, and trash bags, freegans are able to obtain food, beverages, books, toiletries magazines, comic books, newspapers, videos, kitchenware, appliances, music (CDs, cassettes, records, etc.), carpets, musical instruments, clothing, rollerblades, scooters, furniture, vitamins, electronics, animal care products, games, toys, bicycles, artwork, and just about any other type of consumer good. Rather than contributing to further waste, freegans curtail garbage and pollution, reducing the over-all volume in the waste stream...When freegans do need to buy, we buy second-hand goods which reduces production and supports reusing and reducing what would have been wasted without providing any additional funds for new production.
...Freegans scrupulously recycle, compost organic matter into topsoil, and repair rather than replace items whenever possible. Anything unusable by us, we redistribute to our friends, at freemarkets, or using internet services like freecycle and craigslist.
By accounting for the basic necessities of food, clothing, housing, furniture, and transportation without spending a dime, freegans are able to greatly reduce or altogether eliminate the need to constantly be employed. We can instead devote our time to caring for our families, volunteering in our communities, and joining activist groups to fight the practices of the corporations who would otherwise be bossing us around at work. For some, total unemployment isn't an option. It's far harder to find free dental surgery than a free bookcase on the curb, but by limiting our financial needs, even those of us who need to work can place conscious limits on how much we work, take control of our lives, and escape the constant pressure to make ends meet.