Artist Trust: http://artisttrust.org/index.php/for-artists/opportunities
If possible, get a subscription to Professional Artist Magazine (formerly Art Calendar), they have a large selection of calls listed each month.
Obviously this list is geared to fine artists. Designers, if you want to submit your work to a variety of websites, I suggest you check out this article. http://www.pixel77.com/top-10-websites-to-submit-your-design-portfolio/