This URL has a heap of classic horror stories. They vary in length and quality, many are exasperatingly *turgid*, some seem to be missing a few words, but they may offer a useful reference and unexpected inspiration.
http://www.redmoonhorror.com/
I used to have it flagged as one of several repositories for the Shadow tales but, when some-one bought up the copyright ahead of a possible film franchise, lawyers forced removal of the original magazine and book tales. IIRC, many of the derived radio plays were not covered by the legalese so stayed on-line, else-where...
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And, yes, the Clark Ashton Smith site is at......
http://www.eldritchdark.com/