Hmm, well, I have to confess I'm only peripherally in the fandom, so you might be better off asking someone who's more immersed for recs, because I don't really know what's considered classics, vs. what I myself have just happened to read and been blown away by. Still:
The stuff I've got bookmarked for Dean/Castiel is here (http://www.delicious.com/innocentsmith/dean%2Fcastiel). And then there's a really excellent trio of gen-ish stories focusing on Castiel's search for God here (http://unoshot.livejournal.com/695.html). And of course you can seldom go wrong with trinityofone (http://trinityofone.livejournal.com/192383.html), Pru (http://archiveofourown.org/users/rageprufrock/pseuds/rageprufrock/works?selected_tags[]=27) or Pandarus (http://archiveofourown.org/users/FayJay/works?selected_tags[]=27).
Alternatively, Delicious-surfing for Dean/Castiel or looking to see what's gotten the most hits on the AO3 has generally served me well.
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The stuff I've got bookmarked for Dean/Castiel is here (http://www.delicious.com/innocentsmith/dean%2Fcastiel). And then there's a really excellent trio of gen-ish stories focusing on Castiel's search for God here (http://unoshot.livejournal.com/695.html). And of course you can seldom go wrong with trinityofone (http://trinityofone.livejournal.com/192383.html), Pru (http://archiveofourown.org/users/rageprufrock/pseuds/rageprufrock/works?selected_tags[]=27) or Pandarus (http://archiveofourown.org/users/FayJay/works?selected_tags[]=27).
Alternatively, Delicious-surfing for Dean/Castiel or looking to see what's gotten the most hits on the AO3 has generally served me well.