With basic electronics of just a fan and a motor, a bubble machine is also a really easy first electronics project. This one I threw together with spare minutes here and there across the period of a week. The longest part was waiting for the centrifugal fan to arrive from Amazon, the best part was making a lot of mess in the Instructables office before realising that the shower would be a better place to blow bubbles while testing.
My bubble machine was made to keep my friends' toddler amused. She loves bubbles but is at an age where blowing them herself is rather hit or miss (not to mention messy). She spent a VERY happy 15 minutes running through and around them in the street outside, afterwhich the adults stepped in to play with heating the bubbles to see if they'd go higher, or experimenting with different bubble mixes to see if any where noticably better.
Earn 3 months pro membership: Anyone who makes their own bubble machine and posts a photo in the comments will get a code for 3 months of pro membership from me.