For the Summer Prompt, there is only one restriction: your submission must also be submitted to Daily Science Fiction (http://dailysciencefiction.com/ ) . Their submission guidelines are below, but you might want to check their web page for any further information, including published stories

Due August 29.  Reviews are due September 12.

Good luck and good writing.

From the http://dailysciencefiction.com/ site:

Story Submission Guidelines
 

ALERT: Please don't submit stories longer than 1,500 words.Daily Science Fiction (DSF) is a market accepting speculative fiction stories from 100 to 1,500 words in length. By this we mean science fiction, fantasy, slipstream, etc. We will consider flash series--three or more flash tales built around a common theme. If you are submitting a flash series, please note that it is a series in your cover letter and at the top of the submitted text in the submission box. Each story does need to stand on its own.
 

We do not accept reprints. Unfortunately, if you have placed a story on your website, where it is open and available to the multiple billion people who have access to the internet, that constitutes publication. We're sorry. No, we don't accept self-published works.

Please don't submit the same story to us and any other venue at the same time. Please don't send us more than one story. Don't send us another until we send you a response.

We pay 8 cents per word for first worldwide rights and for nonexclusive reprint rights. Additionally, we reserve the right to pay you more money for additional reprinting in themed Daily Science Fiction anthologies.

First publication sounds simple, but in today's fractured fiction market it is anything but. Here's what we mean by first worldwide rights: Your story will be distributed by email to our (free) subscription list, it will then be available on the website, via RSS, eventually through kindle and iphone/ipad (the "issue" consisting of all stories published during its calendar month), and as archived on the DailyScienceFiction.com website. The nonexclusive reprint rights are anticipated to apply to the omnibus volume of DSF's stories for one year. Themed anthologies are anticipated to consist of 50-100% material originally published on DailyScienceFiction.com, plus additional materials as contracted. For these anthologies, payment will be determined if and when they occur.

Not So Helpful Hints

• We need short short fiction, especially flash fiction. Among our featured stories, a shorter tale will get an extra nudge on the scale when weighed against a longer one. This is both for financial reasons and because it matches the preferences of a plurality of our readership. Not fair? Perhaps. Consider yourself forewarned.
• Of course, we want your stories to ooze originality, but a well-written story is a must. We are fond of character-driven fiction, though readers point out that not every story we publish fits that rubric. Our goal is to publish the best stories we can that will be interesting, worthwhile reads. Some stories, especially in the short short fiction, will succeed despite lack of plot, character, punctuation, what-have-you.
• We may purchase dark fantasy, but try not to publish pure horror. We don't mind feeling the flush of arousal, but will not publish erotica. Guns a-blazing might make our day, but we don't suspect most military SF will win us over. Humor? We take it, It often works especially for short short fiction, but do keep in mind that one alien's funny bone is located near another species' sac of indifference. We're likely not your best market for longer funny tales.
• We don't accept multiple or simultaneous submissions, but we promise to be as prompt as possible with our responses. Query if you haven't heard back in four weeks. Or better yet, check your story's status on this website. There is now a "check status" option on the sidebar.
• PS We'd like to emphasize that guidelines aren't worth the paper they're printed on (which in this case is no paper at all). Splurge for a free email subscription, or if you can't afford free, browse the archives here on the website. Read, and get a feel for what Daily Science Fiction publishes. We always want new and different work, of course, but you can get a real tactile sense of this or any other publication only by reading it.