clipped from: www.marketingcharts.com 
More than three-quarters (78%) of adult online consumers in the US made some type of purchase over the web in the previous six months, and the top transaction categories are travel, credit-card management and online banking, according to (pdf) a survey from Nielsen Online.
The #1 online transaction category was travel, with 38% of adult online consumers making at least one travel purchase on the web in the previous six months. Credit-card account management and home banking took the #2 and #3 spots, with 36% and 35% of consumers conducting transactions, respectively.
Clothes, shoes, accessories and books were also popular online purchases.