This document discusses the use of web annotation in an open education environment at Universitat Oberta de Catalunya (UOC). It describes how UOC is an online university that provides open courseware to over 45,000 students. It also discusses several annotation use cases, the impact of annotations on open courseware for collaborative knowledge building, tools that were evaluated like Diigo, and UOC's own web annotation tool called UOCLet. Future developments aim to reduce teacher workload and facilitate easier student use through a more integrated and intuitive annotation interface.