How to organize Eclipse - Workspace VS Programming languages
The plug-ins are stored in the Eclipse installation, not in the workspace folder. So one solution would be to different Eclipse installations for every task, in this case only the required plug-ins would load (and the others not available), on the other hand, you have to maintain at least three parallel Eclipse installations.
Another solution is to disable plug-in activation on startup: in Preferences/General/Startup and Shutdown you can disable single plug-ins not loading. The problem with this approach is, that this only helps to not load plug-ins, but its menu and toolbar contributions will be loaded.
I use Eclipse for programming in PHP (PDT), Python and sometimes Android. Each of this programming languages requires to run many things after Eclipse start.
Of course I do not use all of them at one moment, I have different workspace for each of those. Is there any way, or recommendation, how to make Eclipse to run only neccessary tools when opening defined workspace?
e.g.:

I choose /workspace/www/, so then only PDT tools will run
I choose /workspace/android/, so then only Android tools and buttons in toolbars will appears

Do I have to manually remove all unneccessary things from each of the workspace? Or it is either possible to remove all?