I only recently discovered that you can buy directional antenna for wireless routers/pci cards. Since i live in an area with high wireless activity (detecting up to 15 networks) i deicided my network was taking as much interferance it could so i decided to get one.
D-Link 6dBi Indoor Directional Antenna - Ebuyer
It has increased & stabalised my network signal loads. To put into perspective, i used to get -55dbi at most when there was a few networks in my area. Then it gradually started to decrease as more networks popped up. last few weeks ive been stuck with it dropping to -70dbi which is always dropping out. After attaching directional antenna, ive got -50dbi with a good strong stable connection.
Now that wireless routers are popping up all over the place coz the broadband companies offer them for free, it might be worth investing in.