Ellery Queen Mystery Magazine welcomes mystery story submissions from new and experienced freelance writers. This is not a quick source of making money, (after writing and submitting your story it can take up to 3 months to hear back), but it can be a very fun rewarding way to get your work published while creating a nice income eventually.
Some of their writer's guidelines include~
Use their online submission form to submit your story (no paper submissions accepted after Feb.14 2011)
After you have submitted your work, a tracking number will be displayed and an automated e-mail confirmation containing this information will be sent to you. If you have not received this e-mail within twenty-four hours, please notify them by e-mail (listed on their website). Your tracking number will allow you to monitor the status of your submission through their website.
2,500-8,000 words is the preferred range, but they will occasionally use stories of up to 12,000 words. Shorter stories are also considered, including minute mysteries of as little as 250 words. Rates for original stories are from 5 to 8 ¢ a word, sometimes higher for established authors. EQMM does not accept stories previously published in the United States.
To learn more, visit the Ellery Queen website and read their complete writer's guidelines.