There are a number of very interesting and useful timelines already available, in addition to those listed here on the Revolutions in Communication web site.
For other timelines and resources see:
The University of Minnesota Media History project – Promoting the study of media history from petroglyphs to pixels.
The George Mason University site, History Matters — A general site for study of history, and the Roy Rosenzweig Center for History and New media, also at George Mason.
The Experimental Television Center’s Video History Project
The Media Justice History Project
The South African Media History Project, a non-profit organized by faculty at the University of Pretoria, the University of the Western Cape, and others.
About.com’s media history timeline — Very brief but includes useful links.
Other suggestions welcome.