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- Wake on LAN or PME can be used to remotely wake up PCs that are asleep or turned off. More information is here.
- 2010-Oct-25: WiFi Direct will allow WiFi equipped devices to directly communicate (sort of like BlueTooth pairing) without the need for a router. 
- 2009-Oct-09: The Netgear WNR3500L is a Linux-friendly open source router, though there will still be a closed-source binary blob for some of the core networking components. Discussed here on Slashdot. 
- 2009-Apr-10: How to use Linux to simulate a slow LAN connection by injecting latency on packet propagation. 
- 2008-Nov-16: OpenWrt.org is a Linux distribution for embedded devices (a simpler, prepackaged version called X-Wrt is also available), in particular a large number of small wireless routers. If you need a small, low-power, always-on computing device this might be an approach to take. It might even be possible to run a Windows Primary Domain Controller (PDC) on one of these using SAMBA 3, see the following:
The procedure for getting a PDC working has been figured out for the somewhat similar NSLU2 device (the LINKSYS Network Storage Link), see the HowToSetUpPDCWithSamba page.  
- 2008-Nov-07: Wireless networking security is now under attack by Nvidia GPUs. Elcomsoft has written a system that can use these cards to accelerate the cracking of WPA and WPA2 keys by a factor of 100. Discussed here on Slashdot and also mentioned here on Engadget. A new attack on WPA-TKIP has been announced that can lead to some compromise in security in as little as 15 minutes. Here is a more detailed discussion of the attack (with further discussion here on Slashdot), along with some useful background material on WEP, WPA and WPA2. 
- 2008-Oct-16: A very small IPv6 stack has been developed, this is targeted at the Contiki OS but, being open source, will probably appear elsewhere in time. This fits in 11K of code and needs about 2K of memory to run, so it could easily fit in may microcontroller chips. 
- 2008-Aug-02: Ottawa, Canada, has a fiber to the home program in test where the home owners will own the "last mile" of fiber. 
A discussion on arstechnica about wiring LAN jacks with some useful tips. 
How to Wire Your Home with Network Cable by HomePCNetwork.com is a good introduction that includes a discussion of the basic tools and tips on pulling wires through walls with a fish tape.
- 2008-Jun-22: LANshack.com has some examples of wiring a home network, including Cat 5e feed-thru couplers, patch panels and wall plates. They have a reasonable guide to assembling a patch cable.