The New Yorker's "Critterati" contest invites you to "take a picture of your pet—dog, cat, ferret, iguana, or any other nonhuman member of the animal kingdom—dressed as a character from literature, and upload it to newyorker.com by October 25th." Gallery | About | Rules | Enter. [more inside]
Smithsonian Magazine is holding its first-ever photo contest, open to all adult non-professional photographers to submit entries in five categories. (Professionals may want to see about freelance opportunities here.) I find it particularly nice that there is no entry fee, and no citizenship requirements. For inspiration you may want to browse a gallery of Smithsonian freelance photographers or view the beautiful (and seasonally appropriate) Ghost Towns by Night Light and pick up a few tips on night photography from the photographer.