I was so surprised when I tried this that it was so simple and entertaining, and that we had never done it before. You REALLY have to try it; your kids will be so fascinated.
1. Cut the bottom off of a small plastic water bottle. (I tried a pair of scissors, but a knife worked better).
2. Cover the end of the water bottle with a piece of cloth. Use a rubber band to hold it on.
3. Dip the cloth end of the water bottle into a dish of soapy water.
4. Put your mouth over the small end and blow slowly and steadily. It doesn't require much pressure at all.
4. See how long you can make your snake! (We made some much longer snakes, but I guess our giddy excitement made them hard to capture on camera :-)
One word of warning: Make sure you only blow OUT. If you inhale, you'll end up with a mouth full of suds. This turned out to be pretty tricky for M and G; so I did most of the blowing.
It's Playtime!