Crowdsourcing has been heating up for more than a year. This hasn’t been lost on venture capitalists.

VCs invested $280 million in 35 crowdsourcing companies last year, favoring early stage startups, but financing several significant later and expansion rounds.

This assessment comes from a new report by research firm massolution. The report is based on data collected from 32 crowdsourcing companies in the fourth quarter of last year.

Clearly, crowdsourcing is a young business. Most vendors and services providers remain startups, with about two-thirds owned by founders and their management teams. But venture involvement is growing.

So, too, is the overall market. The report found annual revenue from crowdsourcing companies rose more than 75% last year to $376 million, topping the 53% increase of 2010. Interestingly, the demand for crowdsourced products and services is highest among smaller companies and startups, not big corporations.

In terms of deal making, half of last year’s deals were Series A financings and a quarter were Series B. The largest transactions include Inrix’s $37 million Series D funding and 99designs’ $35 million Series A funding. TaskRabbit closed on $17.8 million, and uTest raised $17 million.

The massolution report says the most active VCs in the space include New Enterprise Associates, Scale Venture Partners, Trinity Venture Partners, Benchmark Capital, Bessemer Venture Partners and Google Ventures. Other firms doing crowdsourcing deals include Kleiner Perkins Caufield & Byers, Foundry Group, Baden Capital, Sigma Partners and Globespan Capital Partners.

Typically founders and their management teams own 68% of a company and venture capitalists hold 13%, the report found.

Of note is that the crowdsourced workforce, which vendors rely on, is growing even faster than revenue. It expanded 100% last year after growing 165% in 2010. In other words, supply is outpacing demand.

Also of interest is that the majority of the crowdsourced workforce is 18 to 40 years old and 60% are male. Most have other jobs and live in developed countries, with the vast majority in North America and Asia-Pacific. Seventy percent participate once a week.

Although the report is based on data gathered from 32 crowdsourcing companies, only 15 of them disclosed financial data. Many of the businesses contacted are focused on the enterprise market. Industry pioneer Mechanical Turk, owned by Amazon, did not participate in the survey.