There are many solutions (all links below point to working solutions with Hudson or existing plugins):
- Hudson Build Status Lava Lamps
- Hudson Ambient Orb
- Hudson Do It Yourself Orb
- "Red Bear Alert!" - The Hudson Bear Lamps
- "Watch the bikes!" - Extreme Feedback with Traffic Lights
- Start to smell those code smells
- Nabaztag
- TuxDroid
- Radiator View (ideal for displaying on a screen on the office wall)
- eXtreme Feedback Panel (even better than the Radiator View, especially for a FullHD flat panel)
Check out the other Build notifiers plugins for more ideas.
Personally, I have experienced the bunny, lava lamps, orbs and the radiator view. They all do the job but I have a little preference for the lava lamps. As Jeffrey mentioned in another answer, it's indeed funny to race against the wax to fix a build failure :)