Monsters University releases tomorrow and you can currently snag a $3 off coupon via Disney Rewards. If your not a member, it's free to join.
The best deal available for this movie is at ToysRUs with the following deal ideas:
Blu-ray + DVD $22.99 or DVD $14.99
Purchase the $10 voucher for $5
DVD for only $9.99 (if you were able to get the $15 voucher before it sold out, it's an even better deal) or the Blu-ray for $17.99 with the voucher price included.