The following resources may be useful to you.
This site is full of useful info for science fiction, fantasy, and spec fiction writers. Here one will find markets for books, anthologies, contests, and all levels of short story magazines from zero pay to professional rates, as well as a study of market response times. Frequently updated. Highly recommended.
Another site listing large quantities of publishers for both print and web medium. Categories are: Prozines, Semiprozines, and Small Press. Not updated as frequently as ralans, but the format of publisher listings is easier on the eyes than ralans.
This site is a search engine for publishers. One can input various parameters (genre, length, pay, etc.) to search for specific markets for one's specific story type. Searching this database has found publishers not listed by the above two listings.
Resources for Writers
The Science Fiction Writers of America
Speculative Literature Foundation
This is a new organization whose mission is to promote literary quality in speculative fiction, by encouraging promising new writers, assisting established writers, facilitating the work of quality magazines and small presses in the genre, and developing a greater public appreciation of speculative fiction.