I have all my computers upstairs in our office (second bedroom), but the telephone enters the house downstairs in the lounge. For the last few years, I've put the ADSL router (Netgear 834G) in the corner and connected to the upstairs using a Wireless Ethernet Bridge (Netgear WGE101). This worked pretty well at first - until I started getting neighbours with wireless!
I first realised that those around me were getting wireless connections when my own LAN kept losing the router. This was quickly fixed by me changing my channel to something unused, but random connection problems still persisted.
The other night I stared in bemusement as the Wireless Bridge claimed a 99% signal strength to the access point on my router, but refused to connect. I remembered a conversation I had with a colleague a few weeks previous where he mentioned that he had installed Ethernet over mains power.
So after T finished watching an episode of Desperate Housewives, I flicked the switch in the fuse box labelled "sockets" and observed that all mains sockets went out - both downstairs and upstairs - indicating that I had a single ring main.
A few minutes later, everything was back (the computers never went down thanks to the UPS! :-)) and I was ordering the Devolo HomePlug Adapter "Highspeed Starter Kit". This arrived last night and consisted of two RJ45 cables and two adapters that plug into the wall socket and have an Ethernet port.
One went downstairs and I plugged the router into it, and the other went upstairs into a four way expansion unit that was not connected to the UPS (I'm guessing that the UPS will clean the signal and could potentially interfere with the Ethernet, but haven't tried it). A few seconds later, and it was all working!
There is some software that can be used to set a custom encryption password for the mains side, and there is even a Linux version included on the CD, but I haven't bothered with it yet.
The unit is rated at up to 85Mbits which is still much faster than the 8Mbit bottleneck of the ADSL connection.
It was running all last night and so far, I am very impressed. The whole thing cost about £80 from Amazon and means I should no longer have to experience the woes of losing a wireless connection at home.