This chocolatey confection not only does a lot of TV advertising, but is also one of about a dozen children's cereals that have their own Web site. Cuckooshow.com lets children explore the set of a "live" talk show with Sonny the cuckoo, watch cartoons featuring the bird and play games. Cocoa Puffs is made by General Mills, whose multi-brand site millsberry.com gets more than 750,000 unique visitors a month under age 18. The average visitor who uses the site visits 2.8 times a month and spends nearly 24 min. per session.