The directory /var/cache/fonts should be used to store any dynamically-created fonts. In particular, /var/cache/fonts/pk will store all of the fonts which are automatically generated by MakeTeXPK.
There should be a link from /usr/lib/texmf/fonts/tmp to /var/cache/fonts. This link allows users to use single path /usr/lib/texmf/fonts/tfm when making changes to their TEXFONTS environment variable. (This is the default path for Karl Berry's TeX tools, distributed from ftp.cs.umb.edu:/pub/tex. (The reason that Karl Berry's tools are mentioned is that they are the de-facto standard for UNIX installations of TeX. These tools are widely used in the free UNIX community.) If another TeX distribution is used, a link from the appropriate font directory to /var/cache/fonts should be made.)
The MakeTeXPK that is distributed with dvipsk will place .pk files in fonts/pk/<device>/<fontname> (e.g., fonts/pk/CanonCX/cmr10.300pk). The .pk files can be periodically purged from the /var/cache/fonts tree, or can be moved into the /usr/lib/texmf tree. If automatic .mf or .tfm generators are used, they should place their data in the mf or tfm subdirectories of /var/cache/fonts.
Other dynamically created fonts may also be placed in this tree, under appropriately-named subdirectories of /var/cache/fonts.