Big Adventure - Bethel. This "adventure center" features a climbing wall in addition to other recreations (laser-tag, mini-golf, water-slides, arcade). Hosts bouldering competitions. - http://bigadventure.com/rockgym.html
Maine Rock Gym - Portland. 24 feet high. 5,000 square feet. Parties. Classes. Also has a portable wall for rent. - http://www.merockgym.com