For the Wicket project we use Maven as a build tool. Today I was building a new release candidate for the 1.2.1 Wicket branch, and I noticed that my MacBookPro was having a difficult time building it.
Looking in the activity monitor, I saw some weird process claiming half my CPU time, thus greatly exercising my CPU. This appeared to be the Mac OS-X spotlight importer. Googling for the process I found a way to shut that process off for a particular directory, so I told Spotlight *NOT* to index my (Java) workspace. This should be a great improvement in performance.
You can tell spotlight to stop indexing particular folders in the settings preference panel for spotlight, on the tab for privacy. Just drag your folder to the list you don't want to be indexed.