Documentation, etc.

BeagleBoard.org - Getting Started
BeagleBone 101
learn.adafruit.com - Installing Operating Systems
Circuitco - Install Ubuntu Desktop
learn.adafruit.com - Installing Operating Systems (Ubuntu)
BeagleBone Black System Reference Manual (pdf)
Adafruit Learning System: BeagleBone Black - Installing Operating Systems
Adafruit Learning System: Copying the Image to a microSD Card
BeagleBone - Creating Sd Card
Boot Ubuntu On BeagleBone Black
SD Card Classes
BeagleBone Demo Files

How to Install Arch Linux on BeagleBone Black

OPKG Package Manager Documentation

Projects

BeagleBoard.org - Registered Projects
Top 10 BeagleBoard Projects
SensorCap Project Page
Adafruit Industries, DIY Electronics and Kits

Capes

circuitco - BeableBone Capes
BeagleBone.org - Capes

Interacto BeagleBone Cape
Get your BeagleBone interactive with a triple axis accelerometer, gyroscope, and magnetometer, plus a 640x480 30fps camera! All sensors are digital and communicate via I2C to the BeagleBone. The camera frames are captured using the PRU.