JPG Magazine has just relaunched. Members can now upload photos, submit to themes, and review other submissions. Contributors get a free year subscription and $100 if they are published. More on how it works here: http://jpgmag.com/about/howitworks.html

JPG is also currently seeking submissions for Issue 7 on three themes: Big, Hometown, and Self-portraiture. 
Photos must be 72dpi JPGs, 2200px wide/tall, and photographers can submit one to each theme.