Funny; I always use the curl command for that kind of thing, since it automatically pipes to stdout -- but there's something fun you can do with that, too:

    curl http://example.com/foo.tar.gz | tar zxf -

Tar's input file is "-", which means stdin. This downloads and decompresses a tarball to the current directory, without creating a temporary file that I have to delete later.

Thanks! Always enjoy adding to my command line tool belt.