Well, I recently changed all my posts on LJ to friends only, HideJournal didn’t work for me (as awesome as it seems it is…) on my Windows computer, and it obviously doesn’t work on my Mac or in Linux…and the original (and I assume more cross-compatible) version of HideJournal doesn’t support tags.

A bit of googling around discovered http://neugierig.org/software/livejournal/hide/ which is a similar but web-based utility that works on anything with a browser. It’s a bit buggy, but it does the job :)