I have a Linksys wireless router (WRT54G v1.1) and found a nifty bios update for it that increases the broadcast power from 14mw to 42 mw. So far no extra cooling is required (only past 50 mw does active cooling measures need to be taken) [side note, any power increase beyond 42mw results in signal degradation and dropouts].
Website : http://www.hyperdrive.be/hyperwrt/
Disclaimer : The following firmware is provided on an "as-is" basis.
I take no responsibility if your device breaks or malfunctions! Use at own risk!
I believe this only works for versions 1.0 and 1.1. Version 2.0 routers may not accept this flash bios. You install it just like you would update the router's bios normally (through the configuration html page). I have been using it successfully for 3 weeks now and no problems so far.
It increases the power output to increase signal strength, range, and clarity. DANGER!: if you don't already have encryption on your router by now, you will want it afterwards. I can sit in my car (powering the notebook) about 5 houses down [about .3 miles] and still have about 50% signal strength receiving from the router. Of course, my notebook's transmit signal is non-existant, but I can sure see my network very clearly. In case you are wondering, this mod does comply with most country's FCC (or similar) regulations regarding communications devices and interference. I believe the limit is at 50 mw to prevent signal bleedover.