The TP-LINK TG-3468 is a 10/100/1000 Gigabit PCI Express network adapter that supports Wake-On-LAN, Auto MDI/MDIX, jumbo frame support, and includes a low-profile bracket for those wishing to install the adapter within a low-profile system. I ended up purchasing the TP-LINK TG-3468 when needing a few Linux friendly network adapters with Wake-On-LAN support for some systems in our benchmarking test farm at Phoronix.
The Gigabit connectivity, PCI-E support, low-profile bracket, WOL, and Linux compatibility is what led me to this particular TP-LINK TG-3468 adapter. I've been using it for a few days now and it's been working out great so I just put in an order for a few more. I figured I'd share my experience should anyone else be looking for a nice PCI-E network adapter that doesn't cost much.
This TP-LINK adapter uses a Realtek RTL8111/8168B PCI Express Gigabit Ethernet controller that is well supported by modern versions of the mainline Linux kernel with the r8169 driver.
Overall, I'd recommend the TP-LINK TG-3468 for anyone needing a Gigabit PCI-E network adapter for spending just over $10. This network adapter can be found at Amazon.com. The PCI version of this Gigabit network adapter is the TP-LINK TG-3269 and it can be found for just $9.