This may be an amateurish question but I'll ask anyway.

I've been working with these two chords

C/Am and F/Dm

I'm looking for a simple three chord progression and those two chords have this sad, sullen, creepy feel to them. I can't figure out which chord they should resolve on. I've tried Am and it works but I think there might be something better.

Any ideas?
Try going to E major then back to A minor. Also, notate those chords properly (I'm assuming you mean slash chord) as Am/C and Dm/F. The way you wrote those implies a polychord.
Thanks for the help everyone

E/D works really well, so does E Major