Posted as of 3.1 Patch. (as things may change in future patches.) I'll try to keep this up to date. ^^
Obvious Things to Know when Playing a Priest ~ Holy Fire Spec blog
http://holyfirespec.blogspot.com/2009/05/obvious-things-to-know-when-playing.htmlJust a lot of "duh" that we can sometimes forget about. ;P Some things are more opinions than others, but still a good list to look at.
Holy to Disc: A Basic PVE Guide - plusheal.com forum, by Vigil
http://www.plusheal.com/viewtopic.php?f=4&t=1476Still needs to be updated with 3.1 information as I link this, but there is still some great info there. I pretty much committed the post to memory before killing Sarth 3d lol. But looking forward to the rewrite.
Healing as Disc Part One: Talents every Disc priest needs holy2shadow Blog
http://www.holy2shadow.net/?p=476Healing as Disc Priest Two: Every Spell a Disc Priest Should Know and Love holy2shadow Blog
http://www.holy2shadow.net/?p=519Pretty much as they describe, great breakdowns of talents and spells to consider when specing.
Priest regen for dummies, without mathbook plusheal forum, Zusterke
http://www.plusheal.com/viewtopic.php?f=4&t=1766Tea with Zusterke: The Groundworkhttp://snarkcraft.wordpress.com/2009/06/02/tea-with-zusterke-part-1-the-groundwork/Tea with Zusterke: Versus @ Snarkcrafthttp://snarkcraft.wordpress.com/2009/06/03/tea-with-zusterke-part-2-versus/Tea with Zusterke: Conclusions @ Snarkcrafthttp://snarkcraft.wordpress.com/2009/06/04/tea-with-zusterke-part-3-conclusions/Everything you wanted to know about Priest regen, and what stats you should be aiming for based on spec. The first 2 Snarkcraft articles list out the formulas and math, and the last part breaks it down to conclude the series.
Best Gear Lists for 3.1 @ Holier Than Thouhttp://www.holierthanthou.nl/2009/05/04/best-gear-lists-for-31/Has links for all specs.
Weight Scales Explained @ Holier Than Thouhttp://www.holierthanthou.nl/2009/05/03/weight-scales-explained/Wanna make your own gear list but confused how?
Compare Gear Easily with Pawn @ wow.comhttp://www.wow.com/2009/01/05/compare-gear-easily-with-pawn/By making your own scales, you can easily compare gear with the Pawn addon.
Plusheal.com ~ great resource for everything healinghttp://www.plusheal.com/<- It's also in the link sidebar to the left. Great community overall, can ask all sorts of things and get some quality advice.
PuG Checkerhttp://www.pugchecker.com/Can that tank REALLY pull aggro off you..? Check them out with this site and see just how uber they really are. (probably a good way to avoid really clueless groups)
Shadowpriest.comhttp://www.shadowpriest.com/How can you be a shadowpriest and not know this forum? D;
Priestly Resources ~ BobTurkey's WoW Bloghttp://bobturkey.wordpress.com/priestly-resources/Lots of theorycraft articles, ui guides, and some other links to stuff
Various blogs: not in any particular orderhttp://www.holierthanthou.nl/http://misery-blog.blogspot.com/http://www.worldofmatticus.com/http://pugnaciouspriest.wordpress.com/http://snarkcraft.wordpress.com/http://www.holy2shadow.net/http://holyfirespec.blogspot.com/http://shadowweaving.wordpress.com/http://violaceousmana.wordpress.com/