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 Experimental Television Center’s Video 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.