It’s old news, but here’s a link to the recent IRS memo on political activity and 501(c)(3) internet activity.

Experience indicates that there are numerous cases involving potential political campaign intervention in the form of communications posted on Web sites operated by section 501(c)(3) organizations. Many of these communications include links to Web sites of other organizations. The analysis of cases involving links on a section 501(c)(3) organization Web site involves determining whether material on a linked Web site is attributable to the section 501(c)(3) organization.