These whole computers on a chip can pack a punch!
adafruit.com the Arduino kit looks interesting, it uses a microcontroller.
Advert for an STMicroelectronics ARM microcontroller with Ethernet support. USB development kit
The Electronic Goldmine said to be a great resource for odd surplus electronics.
crystalfontz Supplier of lcd displays (referenced on slashdot)
Best Electronics Kits For Adults?
US Navy Electricity & Electronics Training Series (NEETS)
arduino.cc LCDLib GPS tutorials
This post on slashdot tells about possible mesh networking schemes, including netsukuku open-mesh.net
He also suggests some antenna types. "As for pringles can antennas, try a bi-quad, a yagi or a waveguide instead, you'll get far superior performance."
From [Wireless Mesh Networking by Tomas Krag and Sebastian Büettrich http://www.oreillynet.com/pub/a/wireless/2004/01/22/wirelessmesh.html]:
The Grid people from MIT have deployed an ad-hoc mesh routing wireless test network called Roofnet link which seems to work for them quite nicely.
To me, their biggest improvement is choosing routes not only based on hop counts and binary availability of nodes (either "available" or "unavailable"), but on link quality, stability and retransmission ratio. This takes the WLAN-specific link characteristcs into account, which differ a lot from regular wired networks where links are either up or down and very less likely flaky.