August 2009: CO-ODE has now officially finished
You should still find most of what you are looking for on the site.
But also see here for ongoing OWL work @ Manchester

Protégé 4.0

The new Protégé 4.0 editor developed by CO-ODE, in collaboration with Stanford Medical Informatics, reimplements a familiar interface on top of the defacto-standard OWL API.

Download

The current release of Protégé 4.0 is available directly from the Protégé website with or without an installer

Please take time to register with them as this helps understand who is using the tool and supports their funding.

Many plugins are already available for Protégé 4.0.

Documentation

User Docs

Developer Docs

Release notes are available for each download.

Status

Protégé 4.0 is now released.

Protege 4.1 pre-release alpha with extra OWL 2 goodness!
Protege 4.1 plugins

Although the pre-alpha is not supported yet, questions should be sent to the p4-feedback list.

Please make sure you backup regularly