Forum graphics, modifications and skins

vBadvanced
Content management system, portal, mods and styles for vBulletin.

vBulletin.org
Graphics, modifications and resources for vbulletin.

phpBB Hacks
Various resources for phpBB, from graphics to modifications and hacks.

IBPlanet
The equivalent of the two previous sites, but for the Invision Power Board.

Forum Images
Forum graphics, primarily aimed at phpBB.

Transverse Styles
Professional IPB, phpBB and vBulletin skins, styles and templates.

NBS Designz
Offer free skins for vbulletin, phpbb, invision and more, as well as web hosting.

phpBB-design.com
Large collection of phpbb themes, ranks, avatars and smileys.

AvatarsX
Quality free avatars for usage in forums and message boards.