Short Story Markets

Electronic Magazines

Ideomancer - http://www.ideomancer.com/guidelines.html

Antipodian (An Australian E-zine) - http://antisf.com/index.html

The Exquisite Corpse - http://www.corpse.org/issue_4/ficciones/budman.htm

On Spec - http://www.onspec.ca/

Planet Relish (speculative humor) - http://www.planetrelish.com/

The Leading Edge - http://tle.clubs.byu.edu/issue39/index.html

Gothic.net - http://www.gothic.net/

Brick and Mortar Magazines

Asimov’s Science Fiction Magazine - http://www.asimovs.com/

Fantasy and Science Fiction - http://www.sfsite.com/fsf/

Analog Science Fiction and Fact - http://www.analogsf.com/

 For Longer Works

Predators and Editors http://www.sfwa.org/prededitors/ - it's got a very good list of publishiing houses and electronic publishers.