Zulily CEO Darrell Cavens wasn't looking for fresh capital. But when the former Blue Nile executive received interest from August Capital for his company's new private-sale shopping service, he decided to pull the trigger. Zulily today is announcing a new $6 million round, which follows a $4.6 million round from Maveron last December.

"We've been very, very excited about the momentum we are seeing," said Cavens, who launched the online private shopping service for kids' apparel, toys and other goods earlier this year. "It certainly wasn't due to us needing it, which is a good place to be." The money will be used to fuel growth, with Zulily expected to nearly double its staff of 40 by the end of the year.

Zulily often gets grouped alongside daily deal sites such as Groupon, Living Social and Tippr. But Cavens said that Zulily is different because it sells actual product on behalf of specialized merchants through private sales that typically last 72 hours. The service -- which offers new specials every day -- offers goods at 30 percent to 70 percent off retail prices. It typically takes about 13 days for customers to receive their purchases, with the company looking to reduce those delivery times going forward.

"As we look at the core private sale space, there seems like there is tremendous opportunity here," said Cavens, whose company competes with Totsy. "We are seeing very, very passionate moms coming to the site and we've seen just phenomenal growth over the past six months."

Cavens -- a former senior vice president of marketing and technology at online diamond retailer Blue Nile -- declined to disclose the number of members Zulily has attracted to date. But Cavens, who co-founded the company along with former Blue Nile CEO Mark Vadon, said that selling kids' gear online represents "an absolute massive market."

August Capital's Eric Carlborg led the firm's investment in Zulily. Carlborg has strong connections to Cavens and Vadon, since the venture capitalist sits on the board of Blue Nile. He is not joining Zulily's board.