My coworkers have been better than me at writing blog articles about OpenIG (at least faster).
Here are a few links :
Simon Moffat describes the benefits of OAuth2.0 and OpenID Connect and how to start using those with OpenIG 3.0.
Warren Strange went a little bit further and with a short introduction to OpenIG, made available on GitHub sample configuration files for OpenIG 3.0 to start using OpenID Connect.
Mark, who run ForgeRock documentation team, describes the improvements done on the Introduction section of the OpenIG docs that we’re making based on received feedback since the release of OpenIG 3.0.