I often work with large projects in Eclipse so I'm frequently using all of the memory allocated to Eclipse. On MacOS X the configuration file is located here:
/Applications/eclipse/Eclipse.app/Contents/MacOS/eclipse.ini
By default the following memory is allocated:
...
-Xms40m
-Xmx512m
...
I've changed this to:
...
-Xms256m
-Xmx512m
...
