Here’s some internet stuff I really like. Given the breadth of knowledge I see from the commenters here, there’s a good chance you’ve heard of most of these. But maybe there’s one you haven’t.
HotSheet has been around since the Internet Jurassic. If your folders are sufficiently organized, you can efficiently use powerful links of many varities. I just use HotSheet as a multi-folder.
TVTropes is a jaw-droppingly deep reservoir of story elements. Click around a bit and you’ll see what I mean. But if you really get into it, it can be dangerous.
Gamefaqs is great, but if you’re a gamer you probably know it already. Do you also know The Escapist? There are numerous good web productions there, reviews and original material.
Likewise for comic book readers and ComicsAlliance. They’ve got several really funny geeks chained up in there.
There are also many supernerds at io9. They will suck up to anything involving the imagination.
Guess there’s a lot more “fun” than “useful” here, huh? Well, Hot Sheet makes up for it.