This is a quick how-to on how we setup a wireless bridge connecting two different LANs in two buildings using 802.11b equipment.
We used the Netgear ME102 Wireless Access Points with the newer BIOS that supports Point-to-Point bridging. Normally two wireless access points cannot talk to each other. Point-to-Point mode, which was normally found on expensive Cisco wireless gear, has come down to the consumer end equipment. The Linksys WAP11 was first to use it, however, apparently as of this writing the new BIOS (2.2?) of the Linksys is extremely buggy. So we went with the Netgear equipment. The price couldn't be beat, buy.com had it on sale for under 90$ each.
Setup was extremely easy. We hooked up each WAP via USB for the first time configuration. The only value changed was to put it in Point to Point mode, and you give the MAC address of the other system. Once both are configured, we hooked each one up to a LAN drop in each building, about 200 foot away from each other. It was going from a three story building diagonally across the street to another three story building. The link instantly came up, the DHCP server in one building was automatically giving addresses in the other. The DSL line also was providing Internet to everywhere. You could log on to the network in the main building also. Since the second building only held about ten people maximum at any one time, this was a perfect solution rather than paying for a second DSL line and separate server and firewall equipment.
Regarding security: Since Point-to-Point mode only allows one WAP to talk to the other WAP specified by MAC address, it would be extremely difficult (though never impossible, of course!) for people to "get in" to the system. However, people could sniff the wireless packets and possibly pull passwords. This is the job for WEP, the wireless encryption protocol. Comes in 40/64 bit and 128 bit versions. There are many web sites out there that have tracked the speed limitations of going with the higher encryption method, but right now we're choosing the 40/64 bit. Another thing to add that isn't necessarily security, but prevents casual hacking, is both the SSID and the Channel selected. The SSID is up to a 32 character alpha-numeric code that signifies "your" network. Only wireless equipment with the same SSID can talk to each other. The channel also helps. There are 11 that you may use in the US. Channels 1, 6, and 11 don't interfere with any other channels, however, that means that anyone with wireless equipment would use them first. So feel free to randomly pick one, and only change it if you get bad interference.
We've had great luck with this, and it definitely beats trying to run cables across the road. If we needed more speed, we can always jump up later to 802.11a gear, which can give 55 MHz or higher speeds.
Update: After about 6 months of running, there have been absolutely no issues of any kind. Its been fast, as secure as can be expected, and easy to use. If you're in a situation that requires a solution like this, I heartily recommend it. Even if you're just tapping into your neighbor's high speed internet solution.