Is it possible to download Snow Leopard? I see that Snow Leopard is available in a box sent through the mail.

Is it also possible to download Snow Leopard from somewhere? So I don't have to wait for it to be mailed to me.
Unless you're part of the Apple Developer Program, or you have access to a server running in an enterprise environment that is licensed to distribute copies of OS X, no.

Since OS X Lion is newly released, you will likely find less and less support for Snow Leopard from this point forward.  Lion is, as of now, distributed ONLY via download, so you may want to consider just getting Lion unless you need Snow Leopard for a spec