A piece of advice: if you're thinking of having a nerd come to your kid's birthday party to make balloon molecules, you'd better have some other entertainment lined up, too.
This buckminsterfullerene molecule takes "only" 60-80 minutes, and the diamond matrix is around 1.5-2 hours.
Sure, tetrahedrons only take 5-10 minutes, but be prepared for an "everyone had tetrahedrons at their party already; you can't do that, it'd be so lame, daddy."
Balloon Molecules [balloonmolecules.com via makezine]
