I've got "Details" by Mieville (brilliant, and optimized for some of my mental habits), some of the stories in Robert Charles Williams' Perseids (reread if there's time), and possibly "A Study in Emerald" by Gaiman (Cthulhu mythos, but is it cosmic?).
So what else would you nominate for cosmic horror? I'm defining cosmic horror as the premise that there's something so alien as to be intolerable concealed under ordinary experience. This isn't the fear of physical attack or the fear of ordinary insanity.
Now that I think about it, some of F. Paul Wilson's Repairman Jack fiction might qualify-- there are two great forces, one utterly inimical, and the other barely indifferent to human life.
If all else fails, I might slide over into whether Charles Williams' fiction would be cosmic horror if it were handled a little differently. The Platonic ideals getting unraveled from the world would be terrifying if I was able to take it seriously.
Anyone know of any fiction that resonates with the fear of ego death (finding out experiencially that what you thought was your mind is just something being accidentally generated) that people who go deeper into meditation that I do are apt to find?
Addendum: Everyone, thank you very much for the suggestions. I'm not sure how much I can get, let alone read, in time for the panel, but at least there will be something to talk about. And if anyone thinks of more cosmic horror, please let me know.