I'm just playing around with setting up a "mesh" wifi access for my entire
neighborhood, and would like to discuss theory if possible.

Am I right in that using a router as an AP only (or bridge) would cut the
bandwidth in half?

And, for experiments sake, I'd like to get an idea of what kind of hardware
to buy to allow access for, say, 100 homes, in a 6 block area.

I know I'd need to convert the AP for outdoor use (I'd like to play with
cheaper consumer stuff), which I can do using an oudoor box and power over
the cat5, right? Although I'd probably design a conduit to carry the signal
and 12V seperately for easier maintenance. Any idea the wattage necessary?
I'm thinking of using PSU's from scrap computers.

Then, how about the repeaters? I need the same brand usually, correct?

I know about the LOS issues, and plan on doing all roof mounts, and USB
client adapters.
Also, any idea of the bandwidth necessary and how to limit it to each
client? (100 users, typical home use).

I bet Jeff has some ideas:)