What's your work environment? Which IDE or whatever you use for code? I will describe mine:
I use Eclipse as my IDE for Rails Java or ColdFusion (I use a separate version/dist of Eclipse for each). I don't have too much to complain about memory usage, cause everytime I prefer spend a hundred bucks more on my pc's to get much more memory that I would use. By the way here's a tip for those who want to reduce the memory usage of Eclipse, or just want to not have some tools that they will not use (that's me!). Download only the Eclipse Plataform Binary (around 40MB) that comes without the JDT and without other unnecessary plugins.
Ok that will save some MB on your memory. Now build your own environment, with only plugins that you want!
Here is mine for Ruby on Rails: Aptana, RadRails, Subclipse.
ColdFusion: CFEclipse, Aptana, Subclipse
Java: WTP, Subclipse.