java -XX:NewSize=100M

... and if you're running on a Server Java VM,

	java –XX:+UseSerialGC -XX:NewSize=100M

Explanation.  HotSpot (1.5 and 1.6) has three garbage collectors:
	- a serial collector (default on client VMs)
	- a threaded (parallel) collector (default on server VMs)
	- a low-latency collector for real-time apps where pausing is bad

I'm finding the serial collector to be faster on OS X.
	To force the serial collector, use 	–XX:+UseSerialGC
	To force the parallel collector, use	–XX:+UseParallelGC

Hotspot keeps newly-created objects in a nursery before moving them  
to an "older object" region.  ECJ makes LOTS of new objects,  
particularly if you're doing GP.  Having that nursery be large is  
quite helpful.  I've found that on Artificial Ant, for example, you  
can double your speed almost with	-XX:NewSize=100M

You can get away with 50M and only have a slight degradation.  Things  
start really dropping speedwise at around 40M.

Your mileage may vary.  Anyone got different results?