I have installed m2eclipse plugin from http://m2eclipse.codehaus.org/. Now I want to use that as a standalone build tool but I am unable to find the installation directory. Can
I am not sure to understand what you want. m2eclipse is a plugin for Eclipse, thus it must be run inside Eclipse.
To have a standalone build tool, I suggest that you just download directly the Maven2 binaries files, and install it on your computer, if it is not already done!
For your information, all plugins are stored in the eclipse-dir/plugins directory, as a subdirectory or as a JAR file.