Well, after my first circuit sculpture I became addicted to this kind of artistic activity. I've got some more ideas. However, it will take some time before I can realize them.
Triggered by the other snowflake (Arduinoflake - how can I put a link here?) of the contest and by the idea to also build something with a 555, I came up with this idea. The coin cell holder in my cristmas ornament is not the most stable one. Therefore I was thinking for some other ways to realize it. I saw a binder clip and immediately had the idea to use it in the battery holder - however in a rather unusual way.
More details soon.
I bent two hexagons out of 1mm wire and used three 1N4148 in three corners of the hexagon to have the two hexagons at a defined distance from one another. I saw this trick in one of the other contest submissions (Hypno Butt).
First I prepared the transparent white LEDs by griding off a bit of the tip and by slightly rougheing the outside of the remaining housing to improve the emission to all directions. Then I soldered them to the two hexagons. One of the hexagons connects all the anodes. The other one connects all the cathodes and is also common ground. I soldered three LEDs to each corner. A central one with long wires and two with shortened wires.
Although there is at least one other breathing 555 circuit in the contest (555 timer LED heart beat) I looked for a simpler solution with only a single 555. I found one on solderpad.com. I used the circuit described there but modified the values of C to 33uF and R to 27k. Mostly because I had them lying around. For the LEDs I used a 100R as common anode resistor. I should have taken a lower one to make it a bit brighter. Maybe 10R would be nice.