Instrutables user Scavix has put together this great step by step guide on building a networked, HD surveillance camera using the Pi and associated components.

Features include:

• Network access to live video
• Storage & upload of recorded video
• Motion detection & alerting
• Night vision (with the IR camera & lights)
• All weather housing
• More

The housing is up to you but the rest is standard Pi components and the Raspian operating system.

(via Lifehacker)