>Dell Inspiron Mini 1018
>Intel Atom N455 @ 1.66ghz
>1gb DDR3 RAM
What's the best Linux distro that'll run reasonably fast on this machine?
OpenSUSE with Xfce is pretty good for low end machines, and is alright for beginners and veterans alike
Lubuntu is good if you're stupid
You can try one of the really tiny linux distros if you really don't mind
Gentoo is a really good choice if you know exactly what you're doing and have patience
If you're really good at computer, you should look into Linux from scratch.
I should also add, that if you're going to want a graphical Desktop environment, Xfce and Lxde are reputable low end ones. I recommend Xfce over the other since it's more comfortable looking and simple, but that's just me.
I like Xubuntu, and it'd run okay on a machine like that. Memory is probably going to be your biggest concern, but Xubuntu uses like 150-300MB RAM idle.
web browsing with a recent Firefox is going to suck a bit though, both due to CPU speed and due to how little RAM the machine has