I've been following your blog for some time as part of my attempt to create the perfect query letter - I want to do this before the manuscript is finished so I won't be tempted to send out a hurried query letter. Do you read science fiction? The reason I ask is because I'm wondering which short story venues, apart from magazines that contribute to SFWA eligibility, would impress you favorably if you saw them on a cover letter. Are you familiar with any magazines so pathetic the title would be a negative?
I do read science fiction. When I do read fiction, it's generally sci-fi/fantasy or historical fiction, unless something else has been recommended to me.
Your question addresses a larger issue, which is credentials. Yes, publications in important literary journals and sci-fi magazines (in this case) are very impressive to us. Your college's literary mag, not so much.
With that said, novel writers out there: Don't stress over short stories if you're not a short story writer. Some people aren't. If you are, by nature, a novelist, then you might burn a lot of time and frustration trying to get some short story that you threw together for the query letter published. The magazines/journals we care about have very, very high standards and way too many submissions to publish everything they would even want to publish.
I made my own foray into trying to get short stories published when trying to sell my second manuscript, which never sold. Eventually I got some short story into an online mag that paid me $5.00, but really, it was an excruciating process. I rarely write short stories and when I do, they're not my best work. All of the different magazines have their own standards and processes and then there's the waiting, waiting, waiting. If you have strong short stories it's worth it, but if it's just eating time that could be spent on another novel, it's not.