Smart's biggest challenger is Promethean USA, which is based in Alpharetta, Georgia. The company says its Activboards are more intuitive than Smart's system. The Activboard technology is supported by a website that shares innovative curriculum ideas among 200,000 registered users, and it is priced in the same range as Smart's product line.

Boards Sold in 2008*: 54,000

eInstruction, a company in Denton, Texas, links interactive whiteboards to hand-held voting systems (think Who Wants to Be a Millionaire?). Students can vote on the answer to a question, allowing their teacher to gauge comprehension. The voting system "is one of the next must-haves," says Colin Messenger, an analyst with Futuresource, a research firm.

Boards Sold in 2008: 10,000

Montgomeryville, Pennsylvania-based Numonics is nearly 40 years old, and it has been focusing on the interactive-whiteboard market since 1993, when CEO Al Basilicato led a buyout of the company. The business goes after smaller contracts and, by offering customers online training, it "sells the benefit of having a more personal relationship with the company," says Basilicato.

Boards Sold in 2008: 9,000

Why buy an interactive whiteboard when you can transform a regular whiteboard into one for roughly half the price? That's the question being posed by Luidia, a San Carlos, California, company that produces a portable device called the eBeam, which renders whiteboard projections interactive. 3M, Hitachi, and NEC use Luidia's technology in their equipment.

Units Sold in 2008: 25,000

The Line: Promethean USA has the most recognized brand in the market after Smart Technologies. Interest in hand-held voting systems could push eInstruction to the front of the pack. But as the weak economy forces schools to cut budgets, Luidia -- the low-cost option -- should accelerate down the stretch.

*All figures represent units sold in the U.S. from January to September 2008.