TemplateMonster.com

BlogFlux.com -- Blog templates

RocketTheme.com -- has a couple of free Joomla templates

JoomlaDesigns.co.uk -- some free Joomla templates here too.

CovantageTemplates.com

TemplatesFeed.com -- free templates

WebPageDesign.com.au

DreamTemplate.com

JoomlaJunkie.com

PixelsParadise.com -- Joomla templates

OhMyFlash

eWebDevelopment Templates

4Templates.com

TemplateOutpost.com

DreamTemplates

a4flash
Flash Templates

Pixelmill
Website Templates

FreeLayout

OpenWebDesign.org

Open Source Web Design

BACWebDesign

ClassyThemes