You've ruthlessly assessed your stuff and separated out the items you're keeping, and you've immediately returned everything that belongs to someone else. So now what do you do with the things you no longer need? Your options vary depending on where you live and the services available, but you really have only four ways to move forward.
Your first notion may be to host a garage sale or sell your stuff on Craigslist or eBay. Wait just a second! Do you truly have the time and energy to sell things in the next week? If not, move on to other options. After a successful cleanse, you don't want a spare room filled with things you'll sell someday.
If you know of someone specific who can use an item, contact him or her immediately. Do not keep things because you're sure that someone, somewhere will want the item someday. If you don't know of a specific person now, move on to other options. Consider free exchange networks. For example, The Freecycle Network has hundreds of grassroots, nonprofit groups around the world. Each local group is moderated online by local volunteers, and membership is free. The network provides individuals and nonprofits an electronic forum to "recycle" unwanted items. Simply send an email offering an item to members of your local Freecycle group.
Most national donation-accepting organizations and charities (such as Goodwill, Salvation Army, St. Vincent De Paul, and others) are interested only in items that are new, unused, or in excellent condition. If you don't have any use for a beaten-up armchair or a broken stove, the charity probably won't either. Visit CharityNavigator.org for detailed evaluations of thousands of charities in the United States and abroad. You'll also find links to charities in your area and info on how donating affects your taxes.
You don't even have to leave your home to declutter. Visit DonationTown.org to find local charities that will pick up your donations and supply you with all the relevant tax paperwork.
If you can't find a person, organization, or charity that can use your item, it's time to (ideally) recycle the item or dispose of it. Visit Earth911.org to find your best options for recycling or disposing of items. Simply enter the items you're getting rid of and your ZIP code; the site lists your options based on proximity to your home. Contact information is available for most options, so you can find out what you need to do to drop off your stuff or arrange for a pickup.