I just picked up a new screen door for the porch today at our local Habitat for Humanity ReStore. It's a brand new door that I bought for only $5!!!. If you haven't checked out your local ReStore yet its a great resource for the do it yourselfer, especially those of us on tight budgets. They carry everything from toilets, tile, windows, doors, lighting fixtures and even entire kitchen cabinet sets at unbelievable prices. It's run by Habitat for Humanity, and the building materials they sell are either new or "gently used" that are donated by local contractors. The money made through the stores goes to the organization's home building efforts. The inventory at the ReStores change weekly, sometimes daily, so I check out our local ReStore whenever I get the chance. It's like going on a treasure hunt for the do it yourselfer.
There are ReStores located throughout the country. You can find your local ReStore by checking out http://www.habitat.org/env/restores.aspx. I've also included a link to the site in my blog's link section to make life even easier.