Gran Turismo 5? If you've got yourself the cash, slap a solid-state drive (SSD) into that puppy and watch the loading times plummet -- at least, so says Phil over on the Beyond3D forums.
Taking two PS3s (an older "fat" with the game installed on a Corsair F120 SSD drive and a Slim with the game installed on its standard SATA drive), Phil timed how long it took for the game to initially load up and checked out several different tracks' loading times in the game's Arcade mode. He found a sizeable, consistent drop in loading times. The biggest factor seems to be the architecture of the SSD itself -- it has no moving parts, so there are no mechanical heads moving around frantically to access the thousands and thousands of tiny, incremental files that make up the Gran Turismo 5 installation.
While SSD seems like it would be better for installing games compared to regular storage, the drives are still costly. Factoring in the affordability of other compatible 2.5" HDDs and the SSD solution seems more and more impractical -- despite the impressive loading times you see above.
Update: Some commenters brought it to our attention that we inaccurately reported the compatibility of some solid-state drives with the PS3 Slim. We apologize for this oversight and have updated the article accordingly.