Webcam as a security camera

Here's a tutorial for you:

How to use a webcam as CCTV

You can also use YawCam.

Features:

• Video streaming
• Image snapshots
• Built-in webserver
• Motion detection
• Ftp-upload
• Text and image overlays
• Password protection
• Online announcements for communities
• Scheduler for online time
• Multi languages

I use and recommend ZoneMinder:

ZoneMinder is an integrated set of applications which provide a complete surveillance solution allowing capture, analysis, recording and monitoring of any CCTV or security cameras attached to a Linux based machine.

It is designed to run on distributions which support the Video For Linux (V4L) interface and has been tested with video cameras attached to BTTV cards, various USB cameras and IP network cameras. A partial list is given in the Wiki and Support sections; please give feedback in the Forums if it works with yours. ZoneMinder also requires MySQL and PHP, and is enhanced by a webserver such as Apache.