Design Calls is a blog blog that provides broad access to a list of open calls for papers (and related announcements) for journals and conferences pertaining to design. It’s run by Fil Salustri (salustri@ryerson.ca).
Its more or less in a test phase and he writes that if there is sufficient interest, he will investigate broadening its scope, primarily by letting other people and groups post their own announcements.
Take a look yourself: http://designcalls.wordpress.com/ it has RSS so its convenient to follow!