I would like to set up my computer so that I can develop in .net, C#, Java, ActionScript,  JS/CSS, and functional languages such as Scala or Haskell.  However, I want to do this with the least amount of full-featured IDEs to learn / programs taking up harddrive space on my computer / running multiple IDEs simultaneously.Which programs can I use to minimize the amount of full-featured IDEs I have to learn/use.  (For example, if Eclipse could handle all of these frameworks, that would be a valid answer)
How do I develop in more languages with less IDEs
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The Jetbrains company has a suite of IDEs with the same ergonomic principles and same keyboard shortcuts and so on.They cover all the languages you're talking about.But most of them are not free though.So my suggestion is:Resharper for C# and .Net: http://www.jetbrains.com/resharper/IntelliJ IDEA for the rest: http://www.jetbrains.com/idea/