The technology choice is a consequence of your needs. If it is a one page web app maybe node.js + JS-framework-at-your-choice, or Rails + Angular.js are good op

The technology choice is a consequence of your needs. If it is a one page web app maybe node.js + JS-framework-at-your-choice, or Rails + Angular.js are good options; if it is a "classic" web app there's plenty of options: Rails, Django, Play (a Scala framework), PHP, Haskell, it's up to your tastes (I would seriously consider Yesod for example, an Haskell web framework); if it is a normal app Haskell, Java, Scala, C, Python/Pypy, Ruby, ... I suggest you to choose some options, play with them for a short time (2 days - 1 week), and finally go for one of them.