The Habitat for Humanity Restore is like the Goodwill of home renovation. If you're doing a renovation, and the stuff you're replacing is in good condition you can donate to the Restore. They take things like doors, cabinets, and light fixtures. They will will sell your old goods and the proceeds go directly to Habitat for Humanity. They also get a lot of brand new donations, typically from manufacturers (for example, when they make a product different from what the customer ordered).
Habitat for Humanity is a great cause -- they build houses for low income families using primarily volunteer labour. What I like best about the charity is that there are no freebies. The family owns the home, but has to pay for it (with money, and labour building houses for other people).
If you're on your way over to Home Depot, it's worth a stop in here to see if you can get what you need on the cheap and help a needy family out at the same time. Or if you're doing renovation, give them a call to see if they want your old stuff.