NASA has a really nifty solar system explorer that lives inside of every single web page describing their various missions.
Ah, that's the cut-down web version. Here's the link for the whole thing: https://eyes.nasa.gov
Chock full of live data from space, wow.
@Cerulean @anthracite Anything inside the orbit of Mars we pay a lot more attention to, classifying them as a Near Earth Object, since that's a potential impact. There's more _mass_ out in the Belt, but there are tons of objects everywhere - Earth has asteroids in its Lagrange 4 and 5 points, so does Mars, so there's a lot of miscellaneous stuff leading and following us.
But also, when the idea of the Belt was getting proposed, we could only see the big ones, and they're further out. :D