I like all sorts of areas, but I guess I excel at Beta-ing Harry Potter, having read thousands of those type of fics (no I'm not exaggerating). Types of stories I like are; romance, drama, action-adventure. Characters I particularly like to read;
Harry Potter - (Remus Lupin, Sirus Black, Hermione Granger, Harry Potter, Albus Dumbledore, Marauder-Fics) Ships; Remus/Sirus, Remus/Hermione, Remus/Tonks, Heck who am I kidding Remus/anyone, Harry/Ginny, Snape/Lily).
Ashes to Ashes - (Gene Hunt, Sam Tyler, Alex Drake, Ray Carling, Chris Skelton, Shaz Granger) Ships; Gene/Alex, Chris/Shaz.
Supernatural - (Sam & Dean Winchester) Ships; Surprise me lol (No incest though yuk).
Torchwood - (Jack Harkness, John Hart, Gwen Cooper, Ianto Jones) Ships; Jack is a bit of a space-whore so I'll read anything but specifically Jack/Doctor(9&10), Jack/Gwen, Jack/Ianto, Jack/John and Owen/Tosh.
Doctor Who - Generally I don't mind old or new.
Basically, anything well written is welcome.