I paid the local "Chalk Master" some cash, so he drew me this huge liquid-chalk ad on the pavement on the busiest intersection in Toronto. here is the time-lapse of the whole process... its quite cool! http://www.torontoforums.ca/tf_timelapse.wmv
Darn, and I was going to go downtown today. I'll look out for it tomorrow, hopefully it'll still be there!
My kids got given some and I let them "go for it" on a window. Hours of scrubbing later... water alone doesn't get it off... cool idea!