In a Windows 7 environment, can 2 neighbors establish a combined, wirelessly connected, bridged network in order to share both broadband access points AND files across a Homegroup environment or the like using a system of 2 modems, 2 wireless routers, wireless access points and/or repeaters, switches, etc? My neighbor and I want to establish ONE wireless/wired network between our 2 homes.
I assume you want to double your bandwidth and that's the reason you don't want to just jump together on one connection. Keep in mind, however, that you may be breaking the ToS of your ISP so be careful!
Anyway. This isn't a typical use case for home consumer products. I'd suggest that you want to do the "merge" as early as possible (i.e. avoid using software to handle it -- do it at the router level). The sooner on the network chain that you turn it into a single connection the less trouble you'll face.
Corporate routers can support multiple connections (or "uplinks") -- Here is an example of a router that can do this: http://www.amazon.com/Cisco-RV082-8-port-100-Router/dp/B0000ZI1FG/ref=sr_1_1?ie=UTF8&qid=1312387502&sr=8-1
Using this type of router you can create a network that is powered across two WAN connections and build up from there.
I don't know the reasons why you want to do this, but financially and security wise it makes more sense to have only one wireless access point, and use that between the two homes. is distance is an issue, you can use an wireless extender antenna to boost the wireless signal.