Jobvite recently published a survey of 600 HR and recruiting professionals wherein 92% of companies who are hiring in 2010 stated that they currently use or plan to use social media for recruiting. Wow!
More than half of surveyed companies have already hired employees through social media, and more than 70% are actively using social media for recruiting.
LinkedIn is the most popular site for recruiting, by far.
The survey methodology may have led to a bit of squishiness in the results, but the study contains a lot of interesting data, and you can download the full report for free on the Jobvite site.