Pablo Bryant asked about mesh networks for dataloggers,

Yes, I do have several applications throughout the reserve and else where. I would like to be able to create a outdoor sensor mesh networking package that I can deploy in a daisy chain fashion to previously inaccessible locations. I have heard that some people flash cheap AP units and turn them into mesh capable units but have not found that way to do it. The systems must be low power, sub 10 watts for radio and datalogger. Any help in this area would be appreciated.

Given that, here are the results I found from some reading and searching. One starting point is inexpensive hardware. The Linksys WRT54GS/L is a good choice, as the firmware is open source and available in many versions. (Info on the Linksys is available from Wikipedia.) A good intro to the Linksys, firmware and project history is here on Wi-Fi planet.

The most common OS for mesh networks is TinyOS, but their hardware support is quite limited.

O'Reilly has a nice document on routing protocols and Linux-based code for ad-hoc networks.

There are a couple of firmware projects that convert the Linksys into a mesh router, so that's sorted. The next problem is how to connect sensors to make it into a datalogger. From this page, we see that you can add serial ports with a daughterboard and there are also other routers that have USB ports available. This page lists possible add-ons to the router, including weather stations, data loggers, GPS, even power over ethernet.

So it looks like the Linksys boxes would work, the software is there but there's work in a) modifying the boxes to add serial and b) software to grab data over serial. A good approach if we're in the 'time but no money' state. From this table, it looks as if there are compatible routers that have serial already onboard, which  removes the PCB/soldering work and then we 'just' have to write software. If we just need basic A/D, something like the $25 Dataq 154 might suffice and code for that is quite far along.