Negative post about Diigo, specifically that new users are apparently asked to import contacts and can end up sending spam to everyone they know.
Long, detailed post about getting started with Diigo with all the things the author likes about Diigo over delicious. She says the networking is the biggest benefit; you know who is part of your network and can easily contact them and share. She also likes the ability to share with groups and Twitter.
Resources for getting started in Diigo and comparisons between Diigo and Delicious
Great visual showing how much simpler collaborating on documents with a wiki is than emailing attachments back and forth. Based on a report of collaboration within the US intelligence community (hence the logo for the wiki side of the table).
Vicki Davis explains that classrooms can’t jump immediately to being fully connected–you have to take steps to build the community and teach the safe behaviors. In 5 phases, Vicki goes from the “intra-connected classroom” to a classroom with many-to-many connections and student management.