Traffic to the Zillow.com Web site is up 67 percent from last year, to an average of 8.3 million unique visitors per month in the first six months of 2009, the company announced.

Other data points:

Of the 8.3 million visitors, 2.1 million in June identified themselves as a real estate professional.

– 44 percent year-over-year growth in page views in the first half of 2009.

– 35 percent more for-sale listings on the site in the first half of 2009 versus a year earlier. In total, 3.6 million listings are posted on Zillow.

– More than 535,000 people have downloaded the Zillow iPhone App since its launch in late April.

– Consumers submitted 265,000 loan requests on Zillow Mortgage Marketplace in the first six months of 2009. Lenders responded with 3.5 million custom loan quotes during this same period.

– The Zillow Directory of real estate professionals now lists nearly 200,000 real estate agents, and more than 12,000

More at the Zillow blog.