Once you get past the lame navigation, this site presents a variety of user-submitted pictures of what could be entrances to Hell. There’s a good mix of modern and ancient locations, and some very fun ones (like this stairway in Mexico guarded by hellcats, which is actually kind of creepy).
Apart from GMing With Pictures, I dig this site for two reasons. One is that these photos make great inspiration for supernatural games, and the other is that I love the idea of a modern world filled with what are, in many cases, very innocent-looking portals to Hell.
It’d be a perfect fit for Dark Matter, Unknown Armies and similar games, and it sounds like a neat premise for a campaign.