I have installed Opt-Out Forums from Get New/Get Daily.
This vBulletin mod allows each forum member to select forums which will not be displayed in theie "New Posts" results.
Some vBulletin.org members are reporting difficulties with this mod, but it appears to be working fine.
I have run this MySQL query to set everyone's accounts to block forum 3 (Politics and Religion) by default:
You can set which forums you don't want to see new posts in by going to your User CP, clicking the Edit Options menu item, and scroll to the bottom of the page.
UPDATE usertextfield SET excludeforumsgnp = 3 WHERE excludeforumsgnp = "";
I also added this line of code to the plugin, to make that the default for all new members:
If you don't want to see Marketplace threads, this is the mod for you!
$vbulletin->GPC['exclude'] .= ',3';