Comment: Don't overthink it. See who needs help and ask how (Score 1) 260
As others have mentioned, there are a number of local entities that recycle/ refurbish / re-purpose old computers. All you have to do is a little looking. In Arizona, a very popular program is Arizona StRUT ( Students Recycling Used Technology) - http://www.azstrut.org/ - look at their website, it might be able to point you in a direction that applies to those in need in your area.
Other ideas: Church-affiliated thrift stores are popular in rural areas. Homeless shelters need computers so their customers can look for jobs / housing resources and stay in contact with family. Boys and Girls Clubs and YMCAs still exist in many urban areas, and may be in need of some equipment. Retirement housing and elderly care facilities may be interested. Look around and ask how you can help.