Continuing analysis of data for Internet Retailer’s 2009 edition of the Top 500 Guide reveals growth for the 151 companies that have broken out web sales so far to be 20.7%-$36.79 billion in 2008 from $30.48 billion in 2007.

The previous week included 131 online retailers with a combined growth rate of 21.4%. The updated report for this week includes 93 web-only retailers, 28 catalog companies, 24 chain retailers and six consumer brand manufacturers.

Web-only retailers continue to be the fastest growing channel, reporting combined sales of $27.94 billion, up 24% from sales of $22.53 billion. With annual web sales that grew by 29% to $19.17 billion in 2008, Amazon dominates the web-only merchant channel and the combined e-commerce sales to date for all online exclusive retailers. Overall Amazon accounts for 52% of all combined sales and 69% of the web-only merchant category.

Even without Amazon, the combined web sales of the remaining Top 500 retailers grew by 12.3% in 2008 to $17.59 billion from $15.66 billion in 2007.

Following web-only retailers, chain retailers grew the next fastest with combined 2008 web sales of $4.47 billion, up 21.4% from web sales of $3.68 billion. Catalog companies grew year over year by 2.3% to $3.98 billion from $3.89 billion and consumer brand manufacturers posted collective sales of $390 million in 2008 from $364.8 million in 2007, up 6.9%.