What your after is called a captive portal they are typically used for 
wireless access but there's no reason you cant use it for a wired link.
googling that should be enough to get you started.

A few suggestions for you.
get an old machine with a decent amount of ram (128mb or so will do)
install the ipcop firewall
install block out traffic addon, That will stop bit torrent and the like 
from running, (99% of portal type software wont stop bt)
find a portal you like and install that (if you still feel the need 
after nerfing bt/etc)
turn on the squid proxy and give it loads of on disk space (4-5GB I 
normally use) and a rather large max object size, if people regularly 
visit the same sites then it can help with bandwidth, typically ~30% or so.

If people need to run bt or the like then you can allocate them a fixed 
IP (via dhcp, so they just plug in and go, no settings change at their end)
and open block out traffic for them.

If you do the allowing of bt traffic (at all), then its theoretically 
possible for some black hat to spoof their mac address and get access, 
but unless you have a bunch of grumpy it nerds its not a large concern.


Justin Richards wrote:
> Hi Folks,
>
> I belong to a community where we live at work on a rotational basis.
>
> A network has been setup where people can just connect to the Internet with
> their private computers in their rooms.
>
> We have problems from time to time where visitors unknowingly connect and
> start up their bit torrent clients and commence massive downloads and
> updates.
>
> However, the bandwidth is a very limited and resource are shared with many
> occupants.
>
> Everyone does the right thing once they have been made aware but short term
> visitors or new arrivals often dont get the memo.
>
> I was at a hotel once and when I initially connected to the inhouse network
> it forced my browser to initially load their webpage.
>
> I would like to do this so they can be advised of the network usage
> guidelines.
>
> Can anyone point me to some links that could help here.  I have tried to
> search "force webpage redirection on establishing network connection" and
> similiar but no such luck.
>
> Cheers Justin
>   

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