[Android Apps and Games] khaytsus:
It's hard to describe what Tasker can do, as there's not much it can't do. I try to describe it like a high-level interface to the Android API. You can adjust hoards of Android settings programmatically based on Events (application, time, date, location, event, gesture).

Personally, I do some of the following:

Passively upload my GPS location to my website every 10m

Have the phone get fairly loud when I'm a home

Quiet when I'm at work

Nearly Muted when I'm in a meeting (matches a Calendar event)

Muted with Autosyncing disabled at Night while I sleep

Disable Rotation on my etext reader to work around a bug in the ereader which loses my position in my book when it rotates!

Make the screen brightness and sounds high when I'm running Waze (gps program) on AC power (plugged into car charger)

... more little things!

All of this is done using an easy to use GUI to build matching contexts and a task to execute when matched. There are lots of samples to start with on the website, and very easy to write your own. Basically it's a graphical programming language that anyone could use.

It's on the market as of today, and the website is here: http://tasker.dinglisch.net/

I have zero connection to the author besides an extremely happy user, decided I would post this here because he's exited beta testing and on the market now.

Here's even a few more examples of things that can be done, pasted from the website.. Still only the tip of the iceberg on things it can do:

passcode-lock sensitive applications (e.g. for child safety)

change phone settings by

application: long screen timeout in a book reader

time: screen brightness lower in the evening

location: ringer volume high at the office, turn off ke yguard at home

wake up with a random song from your music collection

Text-to-speech; read out loud: incoming SMS/ phone number, WiFi/Bluetooth status, when it's time for an appointment, when the battery is low etc etc (Android OS 1.6+ only)

launch a music application when your music SD card is inserted, otherwise a file browser

start the day with a particular application showing

change all your home icons and wallpaper every day, or in particular locations

turn the phone upside down to return to the home screen, tilt 90 degrees to the left and back to toggle speakerphone during a call

create a Home widget to

toggle bluetooth/wifi on/off

launch wireless settings dialog

show a menu of tasks to choose

send an emergency SMS with your GPS location

remap camera etc buttons to other applications, or show a menu of applications and/or actions

decrypt/encrypt and/or zip/unzip application data on the fly when an application is launched/exits

pause music playback while in a particular application, restart on exit

change the Home icon for any application

take a time-lapse photo series (possibly 'secretly')

make a regular backup of a file on the SD card

track your phone location via SMS in case of theft

extend the use of the media button on your headset: take a picture from a distance or go to the previous media track with a long press

record call times and destinations to the SD card

show a popup when an SMS arrives from a particular phone number

setup a birthday SMS to be sent months before it happens so you don't forget

record battery levels over time to a file on SD card

make automatic recordings of what you say during phone calls to SD card

during the night, turn on airplane mode to conserve battery/reduce radiation, but turn it off every 15 minutes to check for SMS/voicemail.

setup a vacation SMS message, with different messages for different callers

launch a music application when headphones are connected