What are you doing with all of these older systems?
Lots of different things. One thing is I use them to teach younger children how to install operating systems, programs, etc. Then let them take them home and keep them.
My 11-year-old daughter knows how to install RAM, hard drives, video cards, etc. because of working on old computers. She has also learned to trouble shoot because of this. She sorts out RAM by type and size, then tests them out using a machine she knows to be good. She has her own "bench testing" station.
PowerPC's like the eMacs still can serve a purpose, like surfing the web, watching DVD's, etc. My daughter's 5-year-old half-sister has a G5 with Cinema monitor that she uses, daily. I put a dozen shortcuts on the desktop, hid the Safari address bar and she can use it to go to great kids sites with games.
Recently, we gave an eMac to an 80-year-old woman. It has iLife '09 on it and she only uses it to store and look at photos. A lot of photos! Having never used a computer in her life, she quickly adapted to being able to search for photos. Her family mails her CD's or DVD's and she loads them up.