DD-WRT is a Linux-based alternative OpenSource firmware suitable for a great variety of WLAN routers and embedded systems. Originally intended for the Linksys WRT-64G (the popular blue router) DD-WRT has been modified to be used with many popular low-cost routers. The DD-WRT firmware adds professional  functionality like:

1. Access Restristions
2. Ad Blocking,
3. Client Bridge,
4. Client Mode,
5. Setup a public hotspot,
6. Commercial grade firewall,
7. Open VPN,
8. Port blocking,
9. Repeater bridge
10. and much, much more!