Light Flow (Lite Version, Full Version) works on the Atrix! It allows you to pick a different color for each application when you get a notification (I set missed call to white, gmail to red, google talk to blue, and google voice to lime). It also works in succession, so if you get a notification from gmail, google talk, and a missed call it will blink red to blue to white. No root is required. The Atrix can do about 10 or so colors. This was one thing I missed from my Nexus One, now made possible!