I want to design a network using wireless bridge for a point-to-mulitpoint connection between five buildings, the furthest is 80 metres away. can someone please advise on if there are bridges which will be suitable for this use and what antenna would be required. any advice would be well appreciated.
Cisco provide the Aironet 1400 series for solutions like the one you are after. The 1400 series wireless bridges support both point-to-point or point-to-multipoint configurations with speeds up to 54Mpbs and of course WEP, WPA and WPA2 encryption modes.
There are of course cheaper solutions in the market (e.g Linksys), but if your planing to provide a professional solution that won't cause you problems, then look no further.
Cisco has plenty of information on the above series, along with setup examples and detailed information that should cover all your questions. You can obtain more information from the following URL:
Just to add to Chris' great recommendation for the Aeronet
For antennas I suggest the following setup, either sector or omnidirectional antenna at the core building and directional or sector antennas at the other buildings.
If you need any more help, let us know. Not to brag about it but my thesis for my BSc was an 11km link using 802.11a