Here's another good site for those of you who like high quality fanfiction that ISN'T slash - the
Tolkien Fanfiction Site. The Short Prose section in the fanfiction archive contains many truely excellent short works - would that all fanfiction was this good!
Also, while the Versaphile site I listed in my earlier post does lean heavily towards slash, the site catalogs its story links by type, so if you choose the Gen category, you can avoid the slash, and nearly all the stories listed on that site are (from a purely technical standpoint - writing mechanics only) well done.
I think a major problem with most fanfiction is that so many of the people who are inspired to write it are really young, and they simply haven't had enough practice at writing yet to produce good work. Writing well is HARD!!! And of course, there are the ones who seem to use fanfiction to work out their sexual issues - please, spare me, I really DON'T want to read that stuff. Porn is boring!