phpiphany is an open source, lean, clean, immaculate and fast HMVC PHP framework.
It incorporates HTML5 templating engine (based on Twitter's Bootstrap 2.0), scaffolding, granular access control, database model, support for all major caching servers (APC, Memcache, Redis), modular plugin structure, state-of-the-art debugger (both code and database), database versioning, Object Relational Mapper and REST API.
More details as well as documentation is coming very shortly.
In the meantime, check out the official website: http://www.phpiphany.com