100th Day Balloon Release (Pre-K-4) Map skills are reinforced when students track the release of 100 balloons (with attached ID tags) on the 100th Day of School.
http://atozteacherstuff.com/lessons/100Balloons.shtml
Powers of Ten (3-4) Students explore the powers of ten in this lesson plan. This site also includes estimating activities (100 jelly beans in a jar).
http://www.miamisci.org/ph/lpextend1.html