To help with self-confidence: Set up areas in your learning community where people can share their perspectives and expertise on subjects outside of work topics. This will provide a place for people to connect across disciplines and enable them to showcase their unique expertise, helping them develop confidence.
To help with self-esteem: Provide fun, extrinsic rewards for contributions (such as clothing, paperweights, or key chains) tied to the initiative and learning community. Rewards of recognition and acknowledgement have been shown to increase motivation.
To encourage participation: Seed the community with content. No one wants to post on an empty forum or be the first to write a blog comment or submit a new idea. Add some innocuous posts, and even some responses, to encourage people to join in with what appears to be an active discussion.
These tips were adapted from the April 2012 Infoline, "Applying Social Tools to Learning," available at www.astd.org/Publications/Infoline.aspx.