Tim Gowers announces the Episciences project, a series of arXiv overlay journals. The platform will be supported by the CCSD, a French documentation center. More details from Jean-Pierre Demailly in Nature. Terence Tao is also on board.
The scientists above are all mathematicians and it is not clear whether (or when) this initiative will also be extended to other disciplines. [UPDATE (23/01/13): According to the CCSD blog (in French), the platform is open to new or already existing journals in all scientific areas. The launch is scheduled for the first semester of 2013.]