I used to use Sveasoft, but their repeated violation of the GPL License, and scare tactics used by the administrators drove me to dislike the company and discontinue use of their products.
I use DD-WRT in my routers. It is free (as Sveasoft should be) and the forums offer lots of How-Tos, Advice, and troubleshooting support.
DD-WRT added a lot of great features such as power boost, NoCat Splash, and even a mod to use the front button on the WRT54G to turn off the wireless radio on the router.
Supported devices as of v23 SP2
* Linksys WRT54G 1.0 CDF0xxx or CDF1xxx
* Linksys WRT54G 1.1 CDF2xxx or CDF3xxx
* Linksys WRT54G 2.0 CDF5xxx
* Linksys WRT54G 2.2 CDF7xxx
* Linksys WRT54G 3.0 CDF8xxx
* Linksys WRT54G 3.1 CDF9xxx
* Linksys WRT54G 4.0 CDFAxxx
* Linksys WRT54G 5.0 (JTAG no longer required, see official documentation)
* Linksys WRT54G 6.0 (JTAG no longer required, see above)
* Linksys WRT54GL 1.0 CL7Axxx
* Linksys WRT54GL 1.1 CL7Bxxx
* Linksys WRT54GS 1.0 CGN0xxx or CGN1xxx
* Linksys WRT54GS 1.1 CGN2xxx
* Linksys WRT54GS 2.0 CGN3xxx
* Linksys WRT54GS 2.1 CGN4xxx
* Linksys WRT54GS 3.0 CGN5xxx
* Linksys WRT54GS 4.0 CGN6xxx
* Linksys WRT54GS 5.0
* Linksys WRTSL54GS
* Linksys WRT300N v1 (v24 beta)
* Linksys WAP 1.0
* Linksys WAP 2.0
* Linksys WAP 3.0
* Allnet ALL0277
* Buffalo WHR-G54S
* Buffalo WHR-HP-G54
* Buffalo WBR-G54
* Buffalo WLA-G54
* Buffalo WBR2-G54
* Buffalo WBR2-G54S
* Belkin F5D7130/7330 (2mb flash)
* Belkin F5D7230-4 v1444 (2mb flash)
* ASUS WL500G
* ASUS WL500G-Deluxe
* ASUS WL500G-Premium
* Mitsubishi R100 Diamond Digital Wireless Gateway (v23 SP2. Rebadged ASUS WL500G)
* Motorola WR850G
* Motorola WR850GP
* Siemens Gigaset SE505
* Ravo W54-RT
* Askey RT210W
* Chipdrive Magicbox 1.1 (beta only right now)
* Chipdrive Magicbox 1.2 (beta only right now)
* Chipdrive Magicbox 2.0 (beta only right now)
* Mikrotik Routerboard 532 (beta only right now)
* Avila Gateworks Xscale (beta)
* all x86 CPU systems, e.g., PC Engines Wrap, Soekris, Desktop PCs, Industrial Embedded Computers based on x86 CPU (beta)