[danpalmer]

Ruby on Rails is a good platform for building applications which are essentially large content management systems, with very relational content. If you can break your application down nicely into resource/data models, then Rails is a great way to build it, and very powerful.

Alternatively, if your application is much more about processes, and data isn't as important, or isn't as relational, Node.js might be a better thing to develop in it. The main problem with Node at the moment however is that it's much less mature than the Rails/Ruby community, and lacks the higher level frameworks like Rails.

I can't recommend PHP for anything at all, unless you've got 10 years PHP experience and don't want to learn a new technology. Although I'm guessing that isn't the case from the wording of your question.

Some other things you might want to consider: Python and Django are similar to Ruby/Rails. I think Rails is a bit more capable, but Django is easier to learn. C# and Microsoft's MVC stack is remarkably good - I usually don't work with anything Microsoft based, but was given a project that required it, I was very impressed.