If you have certain models/versions of routers, you may be able to install some 3rd party firwmware which can add features and boost performance of your router, as well as gain some stability.
Some of the popular routers which these firmwares are available for.....the Linksys wrt54g series, and some Asus and Buffalo Tech routers. Note that you need to be careful of "versions".
//insert "Use at your own risk" words of caution...you can brick your router with a flash gone bad..and render it useless.
You can get features such as
*Increase your wireless output for increased range
*Increase in bridging and WDS support
*AP mode, flip role of WAN/Internet port to 5th switch port
*Overclocking the CPU
*IDS and antivirus scanning of traffic
A basic one which has the look and feel of stock Linksys firmware...
A very popular one which adds quite a few features...
Another cool one that has a nice looking web admin, traffic charts, etc
This one I believe is relatively new.....and it really captures my interest because it introduces some enterprise like UTM features such as antivirus and Snort intrusion detection features..you'd only find on high end enterprise grade hardware that costs thousands, or on some of the better linux distros such as Endian or IPCop with the Copfilter add-on.
I'm listing the popular ones up above...DD-WRT, HyperWRT, and the growing Tomato. There are some more openwrt and various projects to be found at these forums at Linksysinfo....