My personal list of top accessibility resources

1. http://w3.org/WAI/standards-guidelines/wcag/ - WCAG standards

2. http://webaim.org  from @webaim - one of the leading providers of web accessibility expertise internationally

3. http://myaccessible.website  - A very nice site explaining a11y in human language by @myaccessibleweb

4. http://nngroup.com/topic/accessibility/ - some articles from @nngroup

5. http://webaccess.berkeley.edu/resources  - tons of resources by @UCBerkeley

6. http://a11yproject.com  - the name speaks for itself. Follow them here @A11YProject

7. http://developers.google.com/web/fundamentals/accessibility/ - some stuff from google

8. http://a11y-style-guide.com/style-guide/  a11y style guide from @cariefisher

Also available on GitHub!
http://github.com/cehfisher/a11y-style-guide

9. http://a11y.me  - a collection of resources about a11y from @davidakennedy

10. http://inclusive-components.design/  - AWESOME blog & book about a11y. I really liked this one!

11. http://getstark.co  - awesome tool for designing accessible sites from @getstarkco

12. http://github.com/Khan/tota11y  - A plugin to check your site a11y

Right now it's not a big list, since I've only started researching this area.

Feel free to add something new!