Plants for a future is totally amazing. This is a free online database created by a British guy who created his own permacultural food forest on a 24 acre property.
After working as a bus driver for 10 years, he decided to move to the country to change his lifestyle. He designed his farm according to permaculture principles with an edible pond, 3 dimensional gardening and the whole nine yards.
He kept meticulous notes on all the plants he planted and compiled them into a database of over 7,000 plants you can eat, make clothes out of, make medicine out of and use to enhance your garden. Best of all its totatlly free.
Check it out: http://www.pfaf.org/index.php