There is a great article on Lifehacker on installing Linux on a Linksys WRT54GL Wireless G Router. This hack enables you to:

  • Boost antenna power
  • Use the router as a repeater or a bridge
  • Create a wireless distribution system (WDS) or a mesh network
  • Run a VPN server
  • Run a VoIP server
  • Run a managed hotspot with a RADIUS server
  • Manage bandwidth use per protocol
  • Control traffic shaping
  • Support IPv6
  • Remotely access router logs
  • Operate the router as a miniature low-power PC, running a variety of Linux applications

This is just the short list! There are more then a few developers out there writing firmware for this, and other models!