To my surprise there are still many tools available to make an old 286 PC useful. I started a search for 286 at Simtel.Net and found many useful shareware programs. For instance:
Full-featured LAN for MSDOS computers, 286+req
RoseMail, PCBoard offline mail, 8086/286 exe's
Multitasking/multiuser environment for 286-586
There is even a free DOS around, see The OS Developers Homepage and The FreeOS page.