You can download the s-abstractions directly from my CVS repository:

http://mccormick.cx/viewcvs/s-abstractions.tar.gz?root=svn&view=tar

To install them, just untar them somewhere in your Pd path, or modify your Pd path command to include them. You can do this by selecting 'File' -> 'Path...' in the Pd menu, or by passing the command line option:

-path /path/to/s-abstraction/

You will need Pure Data itself in order to use these abstractions. You can download it from Miller's site.