An unknown Harmony fan runs this excellent, automatically updated archive of Harmonian fics, all of them presented as single HTML files. They have good taste too so by going here you’re accessing mostly better quality fics. You’ll also find some fics that have been taken down by their authors on other sites (I particularly recommend Harry Potter and the AUDH). Finally, there’s a useful tagging system for sorting the stories thematically (alternate universe, wrong boy who lived, weasley bashing, etc). The NHR tag indicates the small number of stories that are specifically non-harmony.
Check this site out - it’s a fantastic resource. Ben (now posting from my own tumblr).