Fortune 500 companies got into the Twittering act in a big way last year, according to a study released by the Society for New Communications Research.

Thirty-five percent of Fortune 500 corporations had an active Twitter account as of last year (i.e., one with a post within the past 30 days), according to the study.

Among the top 100 companies on the roster, 47 percent had a Twitter account. Twenty-two percent of all Fortune 500 companies had a “public-facing corporate blog,” and more than eight in 10 of those linked directly to a corporate Twitter account.

Four of the top five corporations — Walmart, Chevron, ConocoPhillips and General Electric — “consistently post on their Twitter accounts,” according to the study, titled “The Fortune 500 and Social Media: A Longitudinal Study of Blogging and Twitter Usage by America’s Largest Companies.” (ExxonMobil was the exception.)

In a breakdown by industry, 13 of the Fortune 500 insurance companies had an active Twitter account, making that sector the most likely to tweet. Eleven of the food-related companies used Twitter.

Elsewhere on the new-media front, the study found 19 percent of Fortune 500 corporations using podcasting and 31 percent using video blogging. The rise in podcasting from the previous year was fairly modest (up from 16 percent). But the rise in video blogging was steep (from 21 percent in 2008). The study did not include comparative data from 2008 for companies’ Twitter usage.

The study was conducted by Nora Ganim Barnes, senior fellow and research chair of the Society for New Communications Research (as well as a marketing professor at the University of Massachusetts Dartmouth), and Eric Mattson, CEO of Financial Insite, a Seattle-based research firm. —Mark Dolliver, Adweek