Here are some I follow religiously:

• http://pinkfood.tumblr.com/
• http://hellyayfood.tumblr.com/
• http://livenudefood.com/
• http://gastrogirl.tumblr.com/
• http://diet-killers.tumblr.com/

Here are some I’ve only discovered recently but which seem pretty good:

• http://bhgfood.tumblr.com/
• http://morefoodplease.tumblr.com/
• http://f00d-p0rn.tumblr.com/
• http://foodfuckery.tumblr.com/
• http://gastronomyfiles.tumblr.com/
• http://stuffed-crust.tumblr.com/