SparkFun PRT-00643 RJ45 8-Pin Connector
These are simple through-hole RJ45 sockets with PCB mounting posts. These 8-pin connectors are commonly used in conjunction with Cat5, Cat5e, and Cat6 Ethernet cables. Because Ethernet cable is so ubiquitous, these are awesome for projects where you need to string a lot of modules together over a distance.
We used these, along with the breakout boards which you can find in the related items below, in the Sound Squid demo!
Note: The price listed is for one jack.