Here is a list of all of the Green Capsules to be found in Disney Infinity's Monsters University Play Set along with where they are and what they unlock.
There are several prank decoration and building texture Red Capsules that unlock items in the Toy Box as well and several toys in the Toy Box that are unlocked only by purchasing the equivalent toy in the Play Set.
On porch at back of rRR House (well, it's a Γ gamma rather than an r so the intention is perhaps GRR).Doesn't actually seem to unlock anything.
Above Dual Pool at back of Frat Row.Unlocks paintball cannon swap for Cannon Base toy.
On side of building bridge north of exit from Scream Tunnel in Fear Tech.
On corner of building next to Botany Labs on west side of Fear Tech.