Apple today released an SMC update for 15 and 17-inch MacBook Pros which addresses fan behaviour under high workload.
This SMC Firmware update adjusts the fan behavior in MacBook Pro systems (15-inch and 17-inch) when running under high workload conditions.
MacBook Pro SMC Firmware Update 1.3 - 833KB
[Update] Due to Apple's ambiguity it was initially unclear which models this update affected, an article on Apple's support site has now been updated to verify that this update applies to MacBook Pro Early 2008 models, MacBook Pro (15-inch, 2.4/2.2 GHz) and MacBook Pro (17-inch, 2.4 GHz).