Few retailers are looking at 2008 as a good year for growth, but there’s one area where expansion efforts could pay off: online sales. The State of Retailing Online 2008: Marketing Report — released last week at the Shop.org Online Marketing Workshop in Scottsdale, AZ — predicts a 17 percent rise for online sales this year, to $204 billion. Biggest categories? Clothes ($26.6 billion), computers ($23.9 billion), and cars ($19.3 billion).

The study of 125 retailers, conducted by Forrester Research, shows increasing investment in search-engine marketing, social-networking ads, and widgets, but decreasing attention on strategies like free shipping. What’s driving the growth, according to Forrester Research principal analyst Sucharita Mulpuru, who spoke at the workshop, is two very different types of online buyer: the comparison shopper on the hunt for deals, and the affluent consumer who’s more interested in convenience than price.

Part 1 of The State of Retailing Online 2008, the marketing report, is now available — where else? — online. It’s free to Shop.org members and $995 to everyone else. Parts 2 and 3, on merchandising and profitability, will be available in July and September.