Oregon makes it especially easy to recycle computers, monitors, and TVs through a state wide problem called "Oregon E-Cycles." It allows these items to be dropped off at no charge to anyone that brings in seven or fewer items. When you do drop off a computer at a location, make sure that all of the data on the hard drive has been securely removed so that it can't be recovered. If you don't know how to do this, then you should get a professional to do it for you. If you leave your information on the hard drive, you leave yourself especially vulnerable to identity theft.
Warning: Deleting files and formatting the drive does not really make the information unrecoverable.
Check out this link for a location near you.
If you don't live in Oregon, please contact your local garbage company and ask them on how to properly dispose of these items.