As a medieval historian with some decidedly old-school habits, Guy Geltner wanted to expand his online presence, but he shuddered at the thought of "friending" or "Tweeting" to get other scholars' attention.

Then a colleague introduced him to Academia.edu, one of a growing number of networking sites designed specifically for scholars.

"Friends told me that it's basically Facebook for nerds, which I'm very happy with," says Mr. Geltner, a professor of medieval history at the University of Amsterdam.

The profile he set up includes far more information than his university's Web page could accommodate, including links to research papers, books, blogs, and forthcoming talks. It lets people know what he's working on and helps him connect with others in his field. "I like the fact that I can read someone's paper without having to be their friend or follower," he says....

Zotero offers similar technical tools for researchers in other disciplines, including many in the humanities. The free system helps researchers collect, organize, share, and cite research sources.

It hosts group discussions, but social networking isn't a major focus of the site.

"After six years of running Zotero, it's not clear that there is a whole lot of social value to academic social networks," says Sean Takats, the site's director, who is an assistant professor of history at George Mason University. "Everyone uses Twitter, which is an easy way to pop up on other people's radar screens without having to formally join a network."...