And also vitamin D3 :)
"d3js" seems to be used for Twitter, Pinterest, Wikipedia and everytime the name as to be standardized to be used, as in URLs. So:
-Official name D3
-Alternate: D3.js, d3.js
-Hashtag: #d3js
-URLs: d3js
-StackOverflow: d3.js
But maybe we could try to avoid:
-Hashtag: #d3.js, #d3 (to help with referencing)
-Name: d3, d3js (to help with branding)