Google Search Techniques for Finding Web-Based Message Boards and Discussion Forums

If you have fond memories of misspending entirely too much of your youth on web-based message boards, or you would like to misspend more of your nights and weekends on them now, Google has you covered.

Simply add inurl:viewtopic.php to any query, and most, if not all, of your results will be discussion threads on boards running atop phpBB.

Similarly, using inurl:'index.php?topic=' seems to get Simple Machines fora, and inurl:showthread.php will unearth vBulletin fora.