I've been looking for the same thing. This website is pretty good, but it's just a list. Doesn't have many great features but it does have most, if not all, of the 3.x monsters and creature collection and tome of horrors, and advanced bestiary by green ronin. Sounds like what you're looking for...
Try the SlyFlourish lazy dungeon master method. That's what I've been using for three years, and it's worked really well. He's got a PDF, a blog, and a youtube series explaining it. Just google "SlyFlourish".