The Gap Inc. has rolled out a line of T-shirts designed by customers of web-only retailer Threadless.com. The retail chain will sell Threadless shirts and bags on its web site and in stores, says Threadless CEO Thomas Ryan.

Threadless.com, No. 514 in the Internet Retailer Second 500 Guide, creates and sells T-shirts and other items that are designed by artists and voted on by site visitors; the winners go on sale. Under the deal with Gap, Threadless will manufacture the shirts and sell them wholesale to the retail chain.

“We’ve always admired Threadless’ democratic approach in sourcing ideas from its community and then letting the community vote for the designs they want to wear,” says Art Peck, president of Gap North America. “We share the same belief that great ideas can come from anywhere, and we can’t wait to give artists another way to get their designs out into the world by selling them in our stores.”

Working with Gap enables Threadless to spread the word about its business model, Ryan says. “This partnership with Gap enables us to not only print more artists’ designs, but also allows us to provide great exposure for these independent artists.” The deal with Gap represents an extension of a strategy Threadless has pursued of late of partnering with other companies, including computer maker Dell Inc. and entertainment conglomerate Disney.

The home pages of Threadless.com and Gap.com today both feature a large image of several Threadless designs with the tagline “Gap + Threadless, Make Great Together.” Gap is featuring 25 T-shirt designs for men and women for $29.95 each and three canvas bags for $25.00 each. On a new category page, Gap posts a link to Threadless.com and encourages its site visitors to design and vote on the next crop of T-shirts that it will sell in stores and online. The designs being sold on Gap.com today are sourced from Threadless.com artists but have never been sold on the site, Ryan says.

In additional to having their designs sold by Gap, winning artists will also receive $2,000 in cash, a $500 Gap gift certificate and $500 to be used at Threadless.com. Ryan did not disclose the details of the business arrangement between Threadless and Gap. He does say, however, that future designs offered by Gap will be sold exclusively at Gap.com and in Gap stores and will not be sold on Threadless.com.

Gap is No. 24 in the Internet Retailer Top 500 Guide.