For the record, I was able to get this working with the following steps:
* Download and install (using installpkg) Fuse http://sourceforge.net/projects/scons/files/scons/2.2.0/scons-2.2.0.tar.gz/download
* Download, extract, and install http://sourceforge.net/projects/scons/files/scons/2.2.0/scons-2.2.0.tar.gz/download
* Download and install (using installpkg) pkgtools http://slackware.cs.utah.edu/pub/slackware/slackware-13.37/slackware/a/pkgtools-13.37-noarch-9.tgz
* Install gcc (from the unmenu package)
* Download and extract the fuse-exfat SlackBuild http://slackbuilds.org/repository/13.37/system/fuse-exfat/
* Download and extract the fuse-exfat source: https://exfat.googlecode.com/files/fuse-exfat-0.9.6.tar.gz
* Run fuse-exfat.SlackBuild
This left me with a package at /tmp/fuse-exfat-0.9.6-i486-1_SBo.tgz, which I could then install using installpkg (at startup).