Via Creative Writing:
1. The Magazine of Fantasy & Science Fiction http://www.sfsite.com/fsf/
This is a professional magazine that began publishing in 1949 which makes it the second oldest continually publishing science fiction magazines in the country. They have one up on the oldest however, popularity. The publication is tremendously popular. It is the most widely read science fiction magazine in the country. It is consistently outstanding and publishing outstanding authors like (from their site) “Stephen King’s Dark Tower, Daniel Keyes’s Flowers for Algernon, and Walter M. Miller’s A Canticle for Leibowitz.” This magazine is the cream of the alien crop.” Fantasy & Science Fiction magazines represents all of what’s best in science fiction today. The publication has an Alexa rating of about 135,000.
2. Analog Science Fiction and Fact http://www.analogsf.co.m/0906/issue_06.shtml
This is a professional magazine that began publishing started publishing 1930 and is as they say “often considered the magazine where science fiction grew up.” They do it very well and have published many outstanding science fiction authors including “Isaac Asimov, Robert A. Heinlein, Poul Anderson, Spider Robinson, Lois McMaster Bujold, and Michael F. Flynn.” The publication is the oldest science fiction magazine in the country, and they are consistently nominated for award after award. This publication has done an unequivocal job over the last 80 years of keeping great science fiction writing alive in print. They have an Alexa rating of about 691,000.
3. Asimov’s Science Fiction http://www.asimovs.com/
This is a professional magazine that began publishing began publishing in 1977 and is simply a high quality science fiction magazine that showcases some of the best in science fiction today. They publish great authors and the publication is one of the best science fiction magazines ever published, hands down. They have an Alexa rating of about 304,000,
4. Strange Horizons http://www.strangehorizons.com
Began publishing in 2000. They are a very popular online science fiction magazine. In 2007 they were nominated for a Hugo award. Works from their issues are consistently chosen for inclusion in many national anthologies. They are a science fiction magazine of the best kind. Strange Horizons represents where science fiction magazines are going in the future. The publication has an Alexa rating of about 200,000.