Google Docs allows students to collaboratively edit documents from any location using web-based programs similar to Microsoft Office while tracking edits. Diigo is a social bookmarking site that lets users tag and maintain online favorites. Glogster enables creating interactive online posters through linking websites, assignments or videos using an easy toolbar. Ning facilitates online social networking by allowing posting, blogging and sharing with adjustable security and collaboration settings. VoiceThread combines voice narration with images such as photos or PowerPoint slides and enables sharing and commenting.