I bought a Brother all-in-one (MFC-240C) printer, fax and scanner. The scanner doesn't work out of the box on Linux, but Brother provides drivers for some popular distributions on their website.

Obviously you can't install the RPMs, and compiling brscan2 from source (see the Brother Linux scanner driver page, http://solutions.brother.com/linux/sol/printer/linux/sane_drivers.html ) you get something like this:
sh makepackage 2  d

Version = 0.2.4
Relese Number = 0

makepackage: line 84: epm: command not found
mv: cannot stat `linux-2.6-intel/brscan2-0.2.4-linux-2.6-intel.deb': No such file or directory
make[1]: *** [brscan2] Error 1
make[1]: Leaving directory `/home/andrei/temp/brscan-src-0.2.4/brscan/mk_package'
make: *** [brscan2] Error 2
This is what you need to do to get the scanner working on Slackware:

Get a copy of alien ( http://kitenet.net/~joey/code/alien/ ). Extract it, compile it, and install it. Then run (as root)
alien -c -t brscan2-0.2.4-0.i386.rpm
That will make a .tgz package of the stuff from the RPM. Then install it using installpkg brscan2-0.2.4.tgz

That's it - the scanner will work now.

Thanks to Brian from the linuxpackages.net forums for giving me this solution.