The short list of tools you should be using if you're building startup web apps. I'm building this list for myself... but maybe it'll help someone or I'll hear of better tools.
HTML + CSS - because you have to
bootstrap - simplifies layout and CSS formatting to give you a huge head start on a slick web page
bootplus - modifies bootstrap to have similar styling to new Google+Yeoman.io - package & deploy
Handlebars - templating
d3js.org - for slick data visualization
nvd3.org - re-usable charts built on d3js
sublime text - text editor with syntax highlighting and way more
niice.co - search for creative material (aggregates Behance, Dribbble, Designspiration, etc)
feel free to suggest more... I will continuously update the post.