A thinner font would be better, and please add .ch at the end of the name. The on/off button idea is good and its design is well done, we like it. Maybe try some more color variations ?
i'm sorry i must withdraw #4, the concept light bulb is claim by nalapraja (because he is first submit with light bulb), i'll try find other idea for your contest and hope you like it and just feel free give some feedback.
The logo of #31 is too imposing, and colors could be better (less numerous?). That's a shame for #4, as we did see it more like an on/off button than a light bulb. Feel free to work around that idea though.