CALCnet allows networking of TI-83 and similar calculators with relatively simple external hardware.
With that detail out of the way, you are free to implement a display-wall and/or the most powerful z80 cluster computer in the known universe.
Extra credit, of course, will be awarded if you succeed in writing an xorg driver that can treat an MxN array of networked calculators as a greyscale display of appropriate resolution.
As the author of that hack, I solidly second that suggestion. We also have a bunch of other calculator hacking projects that might interest you, like case-modding, adding features likes backlights, PS/2 ports, a touchpad, etc. There was the FloppyTunes project ( http://www.cemetech.net/projects/item.php?id=38 ) that lets you play music on a floppy drive with a calculator. Since you have so many calculators, though, CALCnet would be fun to play with, and since we're always looking for people to help with a wireless version of CALCnet, that might be something fun. And no one has written a distributed computation system with CALCnet yet!
A list is only as strong as its weakest link. -- Don Knuth