Upgrading to Linux from a VX Works Router
Source: Jeremy Collake & BitSum.com

Linksys' decision to move to VxWorks was not a good one. Among the biggest selling points for WRTs was the option of changing firmware. So when Linksys released the WRT54G version 5, many Linksys fans were disappointed. If you had a JTAG/ serial interface on your version 5, a way was found to upgrade to Linux-based firmware. Adding another interface to a WRT was too difficult for many. Thus, they either needed to buy a WRT54GL or stick with the buggy VxWorks firmware. However, a work-around has been found and now new WRT54G and WRT54GS owners can use Linux-based firmware!

WARNING: This Process May "Brick" Your Router!

If you have a WRT54G Version 5 or 6...
1. Download linux_prep_wrt54g.bin
2. Go into 192.168.1.1, click "Administration".  Go to "Firmware Upgrade", and select the linux_prep_wrt54g.bin file. (see here for help) Click Apply and wait a few minutes.  After you're screen turns white, power cycle the router.  
3. Download linux_upgrade_wrt54g.bin
4. Go back to 192.168.1.1. You are now in Management Mode.  Select the linux_upgrade_wrt54g.bin file and upgrade.
5. Again, power cycle the router. When restarted, the Power LED should be flashing.
6. Download tftp.exe
7. Download dd-wrt.v23_micro_generic.bin
8. Open the TFTP client (Enter IP: 192.168.1.245 or 192.168.1.1) and upload "dd-wrt.v23.micro_generic.bin"

9. The router should restart.  Wait a moment and than go to 192.168.1.1.  If all went well, you should be running DD-WRT Micro.
10. Enjoy your new Linux router and have a Cold Beverage!

Help? Click Here for Notes and FAQ

If you have a WRT54GS Version 5...
1. Download linux_prep_wrt54gs.bin
2. Go into 192.168.1.1, click "Administration".  Go to "Firmware Upgrade", and select the linux_prep_wrt54g.bin file. (see here for help) Click Apply and wait a few minutes.  After you're screen turns white, power cycle the router.  
3. Download linux_upgrade_wrt54gs.bin
4. Go back to 192.168.1.1. You are now in Management Mode.  Select the linux_upgrade_wrt54g.bin file and upgrade.
5. Again, power cycle the router. When restarted, the Power LED should be flashing.
6. Download tftp.exe
7. Download dd-wrt.v23_micro_generic.bin
8. Open the TFTP client (Enter IP: 192.168.1.1 or 192.168.1.245) and upload "dd-wrt.v23.micro_generic.bin"

9. The router should restart.  Wait a moment and than go to 192.168.1.1.  If all went well, you should be running DD-WRT Micro.
10. Enjoy your new Linux router and have a Cold Beverage!