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Now that NDA has lifted, I'll keep adding links to Skill line descriptions and calculators as I become aware of them.
First of all, a huge thanks to the Tamriel Foundry (http://tamrielfoundry.com/) THE, premiere ESO fan site, for being the first to post this without breaking NDA.
Eldersouls, another fan site was full of NDA breaches including leaked videos, etc. I've been aware of their rather good skill database project for a long time but I didn't link it before for obvious reasons. This one now also includes the Werewolf and Vampire skill lines. It can be found here: http://eldersouls.com/elder-scrolls-online/skills
This list of skills is nicely laid out and seems to be more accurate than the others...nicely laid out too: http://elderscrollsonline.wiki.fextralife.com/Skills (Thanks to Castielle101 for this one)
Class build articles
Putting this one on top. It's the best and most complete Build Planner so far: http://esocalc.com/ (thanks to HighMarshall for the heads-up)
A couple of months ago someone developed an outstanding skill calculator UI that lets you theorycraft builds a bit. Here it is: http://skillcalc.massyx.de/
EDIT: an even better skill calculator - http://esohead.com/calculator/skills
Edit: a 3rd calculator at the Mostly Harmless Guild site that also looks pretty good (thanks to gestalt11 for finding this one): http://skills.tesotools.com/
And a 4th one (thanks GW2Life) http://teso.mmorpg-life.com/eso-skill-calculator/
A word of caution: Some of this info is incomplete and dated. Every beta weekend there are many changes to all of these abilities as they balance them preparing for launch. So take them for what they are, early efforts, and especially take the hard numbers (Magika or Stamina cost, range, damage numbers, CC length, etc.) with a grain of salt.
I'll keep adding links and making edits as needed as I become aware of changes.
NOTE: the Tamriel Foundry links below is the original pre-NDA list from this thread.
Ranged Weapons: http://tamrielfoundry.com/2013/10/skill-overview-ranged/
Melee Weapons: http://tamrielfoundry.com/weapons/
All armor skills: http://tamrielfoundry.com/2013/10/skill-overview-armor/