How do you think category support should be implemented in
nanoblogger?

So far I have categories setup as sub-directories in a special
category directory. An index.html is created within each category's
sub-directory that includes all of the entries for that category.

From the command line, categories are handled much like entries are
currently handled.

e.g. "nb -b weblog/test -c 1 -e 4" would open weblog/test to edit
entry id number 4 of category id number 1