The main Subversion Repository provides a web interface allowing developers to browse the repository. This interface uses the ViewCVS software; please consult the documentation there for using its features.
Many Zope-related projects have mirrors of the “trunk” of their project in Subversion imported into Launchpad as Bazaar branches. These imports provide a web interface as well, allowing developers to browse the source, the changeset history, and any outstanding merge requests. See for instance the ZTK project group’s branch overview:
and the “zope.org” project group’s branch overview: