The best part though is that you can download apps from the market that do nothing but add even more conditions and settings to Locale, such as: headphones plugged in or not; whether the phone is on a car dock; launching other programs; lockscreen passwords; and many more.
As an example of what it does for me:
Default settings: Wifi off, Ringer volume 85%, Media volume 70%, Password Lockscreen on.
At home: Wifi on, Lockscreen off
At work: Wifi on, Ringer volume 0%, Vibrate on
At night (10pm-7am): Ringer volume 0%
Headphones plugged in: Media volume 20%