There are some incredible and fun prompts up at
multiverse5000. Go and
claim a few if you haven't already. There is no minimum word limit, and some truly inspired crossovers.
I've already put in for mine, which I'm terribly excited about.
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In the meanwhile, spotted from someone lovely on my flist (I've done a quick scroll through and can't find the post-- sorry, kind reccing person!) I've discovered
shati's
Good Omens fic. Every single one is worth a read-- they're short, deftly written, witty and sweet. And all feature Crowley and Aziraphale.
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I've also had my eye on
sga_genficathon. The entries are just being posted now, very much looking forward to enjoying the team-y goodness that will no doubt ensue.