Yahoo! Inc.'s [YHOO] courtship by Microsoft Corp. [MSFT] hasn't stopped it from doing business. The company was the lead investor in a $20 million Series B round of financing in mobile search company Vlingo Corp. The round also included existing investors Charles River Ventures and Sigma Partners, which previously invested $6.5 million in the company.

In conjunction with the deal, Yahoo! on Wednesday launched a voice-enabled version of its oneSearch service that allows users to speak their query as if they were typing it into a search box.

Vlingo said it would use the funds to expand its operations overseas and continue product research and development. The company said its future plans also include placing its technology across a broad range of mobile phones in the U.S., though Yahoo! has exclusive use of the technology.

There's nothing like getting one of the largest Internet companies to not only invest in your company, but agree to use its technology as part of its search operations. If Yahoo! is absorbed by Microsoft, however, it's not clear if the relationship would survive. Last March, Microsoft said it would acquire Tellme Networks Inc., which also provides voice-enabled mobile search.

Yahoo! divulged its plans for Vlingo and mobile search Wednesday at the CTIA-The Wireless Association conference in Las Vegas. The company is promising "instant answers to any query," not just through web links.

See March 2007 statement from Microsoft
See April 2 post from GigaOm
See April 2 story from News.com