[nocte]

take this code:

RewriteRule ^([a-z0-9-]*)-t([0-9]+)\.html$ /showthread.php?t=$2 [R=301,L]
RewriteRule ^([a-z0-9-]*)-t([0-9]+)p([0-9]+)\.html$ /showthread.php?t=$2&page=$3 [R=301,L]
RewriteRule ^([a-z0-9-]*)-f([0-9]+)\.html$ /forumdisplay.php?f=$2 [R=301,L]
RewriteRule ^([a-z0-9-]*)-f([0-9]+)p([0-9]+)\.html$ /forumdisplay.php?f=$2&page=$3 [R=301,L]

that should work for thread and forum views (with and without pagers). If you delete the "$"s the rules will work for URLs with (eg. highlight) parameters too. I don't know if there's a downside doing this - propably not.