You could spend money or you could spend some time optimising your wireless setup.
Raise the router above furniture level, experiment with channels, choose a channel 5 stops away from strongest neighbouring wifi, relocate cordless phone base or video sender away from computer or router.
I am also interested in this question. I work in a small security booth and all i get is a one to zero bar signal and i was experimenting with store bought wireless extenders (aka the cisco wireless usbs that come with the usb to usb extender) but none has seemed to work. I am still doing some research and some searching on the net on how to *catch* a better signal. If i find anything i will defiantly fill you in.