A few months ago I brought my family's old Macintosh SE/30 to my home office. While it booted fine a few years ago, it looks like mine has developed SimasiMac, which means a trip inside the machine to replace a few capacitors (I hope). Along with the SE/30 I brought a Powerbook 540c, one of the more capable (and last) of the smaller, 68LC040-based laptops from Apple. The 500 series had numerous firsts, like a trackpad and sleep mode when you shut the lid, plus you could upgrade the CPU to a PowerPC chip.
Currently our 540c doesn't have much software on it, as we used Zip disks to store many of the educational programs my little brothers used in the 90's. It does, however, have a copy of SoftPC, and Windows 95 installed on it. Not two months ago my son sat here in the office and had a ball playing with Paint (why isn't there something like this pre-installed on Macs, hm?) and Minesweeper. He's playing with the calculator in the picture. I find it a little sad that we had to resort to Windows for casual fun, but I guess that's why Macs were never considered "toy computers" (that's sarcasm for those who missed the reference).
When the kids do play classic Mac OS games, I let them use my 500 MHz G3 iBook (the first of the "icebooks"), which not only runs Mac OS X and Mac OS 9, but has a version of TuxPaint for OS X, which I highly recommend. It should be noted that quite a few older Mac educational games won't run on the iBook. Often it's an issue with older versions of QuickTime expected by the program, or some funky extension or Director call that just won't work after OS 8.5 (remember Sherlock?).
You can see some really old Macs pulling serious duty over on Cult of Mac as well. But I want to know what you readers are running in the way of older Macs. What's the oldest Mac currently still living in your house, and what do you use it for? Oh, and if anyone has a copy of NetTrek they'd like to share...