If you are using RadRails when developing your Ruby in Rails applications you will be interested in increasing performance. Christian Pelczarski has an interesting instruction on how you can boost performance of the Eclipse/RadRails combo by switching to the latest Sun JVM (version 6.0) for Windows XP.
You can usually get some extra performance by setting the initial heap size and the max heapsize to the same, thus bypassing the dynamic growing/shrinking of the heap.