Hacktivate

Updated
This is just a quick bit of techie documentation capturing what I did. I figured most of this out thanks to:
http://csircoin.blogspot.com/2005/06/setting-up-olsr-mesh-on-linksys.html
Florian Walther and a bunch of other guys from olsr-users at olsr.org.

Here is my plan: Take a bunch of Freifunked WRT54Gs and disperse them around the neighborhood, preferable on rooftops with antennas. Some of these would be connected to VSAT systems and therefore provide a route to the web. Then whoever wants to jump on the mesh, just turns on their machine and connects with normal DHCP to the ad-hoc network supplied by the mesh.

Here is my step by step:

Take a stock WRT54G, connect to it via the web interface. Upload the freifunk firmware. It will reboot, then you can connect to it on the same address: 192.168.1.1. You will do this for all of your WRT54Gs (if you only have one or none, for that matter, you can still build a mesh network with a PC running the OLSR.org software).

Next I configured the boxes to have sane IP addresses, to offer separate blocks of IP addresses to clients, and to maximize the distances they cover. Here are the settings. I copied most of the plan from Florian's topology diagram. Here are the changes I made from the default settings:

OLSR
OLSR DHCP: 104.3.2.0/26,255.255.255.192

Wireless
WLAN Protocol: Static
IP Address: 104.3.2.1
Netmask: 255.0.0.0
WLAN Mode: Ad Hoc (Peer to Peer)
ESSID: Lil-Mesh
TX Power: 84
Radio Mode: B Only
Transmission Rate: 1 Megabit/s

LAN
LAN Protocol: Static
LAN IP:192.168.5.1
Netmask: 255.255.255.0
Disable Firewall: Checked

WAN
WAN Protocol: DHCP
Hostname: lil1-wrt54g

The second and third boxes were similar. Differences for the second box:
OLSR
OLSR DHCP: 104.3.2.64/26,255.255.255.192

Wireless
IP Address: 104.3.2.65

LAN
LAN IP:192.168.6.1

WAN
Hostname: lil2-wrt54g

Once that is done you can power up all of your WRT54Gs. If you have an internet connection from a DSL modem, or a shared internet connection then plug that into the internet port of one of the WRT54Gs. The mesh will then calculate all of the optimum routes to one another, including routes to the closest internet connection. Now connect your clients to them with either an ethernet cable or with a wireless connection. Finished!

Update:
I found that I didn't need any of the HNA entries - and also turning on NAT made things simpler. I just successfully googled from a neighbors house about 1/4 mile away using the mesh. I am on my way!