Using an Apple Pro speaker, I made a flashing RGB LED iPod dock for about $35.
I recommend reading the entire 'ible before starting. Also, note that the volume is control from the iPod.
It consumes minimal power in shutdown mode, and is controlled by a Teensy.
This took me ~3 days to build, and you should know how to solder pretty well before doing this project.
The enclosure looks amazing when lit, it is really fun to watch it.
Step 1: Gather Tools & Materials
Hot Air gun/Hair dryer
Hot glue gun/epoxy
Drill (or dremel)
Sandpaper (fine grit)
(1) Teensy 2.0
(1) Sparkfun RGB LED breakout
(1) Sparkfun Mono Audio amp breakout
(1) Apple pro speaker (You only need one speaker, not the set)
(1) Mini-USB cable (will be cut up)
(1) iPod-USB cable (also will be cut)
(1) Audio plug
(1) Push-on/Push-off button
(1) 10K ohm resistor
(1) Roll of solder
(1) Headphone foam cover (black foam circles found on old headphones, I had a few lying around.)
Assorted heat shrink
Ribbon cable or other thin wire