Skyfire Labs Inc., makers of the “game-changing” Skyfire mobile browser, announced today that they have raised $13 million in Series B funding. This round of funding is led by Lightspeed Venture Partners, and includes previous investors Matrix Partners and Trinity Ventures.

This brings the total funding up to $17.8 million, following a $4.8 million Series A round in June of last year. As part of the deal, Jake Seid, Lightspeed’s Managing Director, will be joining Skyfire’s Board of Directors.

Skyfire is a mobile browser which offsets a good amount of the page rendering workload to a server, freeing up the handset’s CPU and RAM to crunch things most mobile browsers leave out — namely, Flash and AJAX. Check out the demo video here.

This additional funding places further pressure on Skyfire’s main browsing rival, Opera Mobile. While Skyfire is (tentatively) free, Opera Mobile goes for 24 bucks. With Opera Mobile 9.5 facing delays, a free alternative with rich media support is beginning to look mighty tempting.