DD-WRT is an alternative firmware which is available for a variety of routers. It is Linux based and adds features to low end routers normally only found on expensive units. I have installed DD-WRT on a Linksys WRT54G and a Linksys (Cisco) WRT160NL, both are inexpensive routers. The upgrade is very simple and involves no more than finding your router on the router database and downloading the firmware file. It is then a simple matter of using your routers standard firmware upgrade option. This has to be one of the easiest hardware hacks I have ever come across. If you perform this upgrade your router will now have features such as IP v6 support, quality of service, the ability to increase the radio power, bandwidth monitoring, dynamic dns, vpn client and server support, the list of features goes on.
The PPTP client is a very useful feature allowing you to create your VPN connection on the router and not your computer. This VPN connection is then available to all computers connected to the router. Of course you can also configure a PPTP server and connect to your home network when on the move.
The radio transmit power in routers is fixed to a set limit to ensure they do not cause interference. In some installs You may just be picking up the wireless network but it is not strong enough to be reliable. Increasing the transmit power could cure this for you. I haven’t tested this aspect of the firmware yet to see how much further away I can be from the router. When it stops raining I may try that one.
Many people have offices separate but close to their residence and in these cases increasing the transmit power may not be enough. In this situation DD-WRT can be configured as a repeater. This will receive your wireless signal and rebroadcast it thus extending the range of your wireless network.
Do some research first because not all features are available to all routers. Some have less RAM etc. I have always used DD-WRT but another firmware Tomato is also getting good reviews. This appears to be more user friendly but not have all the features of DD-WRT. I would be interested to hear from any users.