5pieces.com
Design focused, tutorials, links.
Koru Productions ExpressionEngine Development
Derek is the number three man on the EE development crew and the guy most likely to solve the really tricky problems that crop up on the forum. He also has a shiny, shiny website with lots of goodies for the faithful fans. Drop in, skim through his offerings, and admire the shiny.
Low Weblog
Of the bad? Most of Lodewijk's site isn't in English. Of the worse? I only speak English. Of the good? Really cute cat logo. Of the best? A very nice selection of plugins and modules, well worth taking a look. There's an Akismet port, yearly archives, a file management module and more. Check the ExpressionEngine category to find them all.
Mark Huot
Mark's been hard at work cranking out some very useful ExpressionEngine extensions- many related to the publish page. He also wins the prise for coolest main site page I think I've seen. Check out his code section for the EE goodies.
pdx : eeblog
Yoshi's LinkList module is powering this list 'o links! You'll find some other handy plugins, such as 'On this day' and the 'Birthday' plugin, as well as a few EE tips and tricks.
Solspace
The Solspace crew is a full service design company, but I link to them here for their excellent offering of ExpressionEngine plugins, extensions and modules. If you're looking for a third party module, be sure to browse through their offerings- both free and pro. And if they don't have it, they can build it.