Update: If you are interested in improving Vista’s performance you might be interested in this post, too: 50 ways to speed up Vista
SpeedyVista has a comprehensive list of Vista’s services accompained by some explanation regarding their purpose. The list distinguishes between the different Vista editions: Home Basic, Home Premium, Business and Ultimate. You can use this list to disable unnecessary services to speed up Vista and, more importantly, as reference guide.
They offer three configuration sets as .reg files: Safe, Tweaked and Minimal:
Safe: Just disables services which do not affect user experience.
Tweaked: Many heavy and most likely unused services have been disabled.
Minimal: All services that are not necessary to every day use and windows update have been disabled.
SpeedyVista also offers the default settings as .reg file. I suggest downloading them too, before applying one of the special configurations. Who knows, you might not be able to access the internet anymore after you messed up your system.
I am always a bit skeptical about tweaking tips for desktop systems. You can find countless such tips on the net for Windows XP. From my personal experience they never really help to improve the performance, they just make your system unstable. Everytime something doesn’t work properly, you ask yourself if your tweaking is the reason. The time you spend to tweak and repair your system usually exceeds the time you gained from the performance improvements.
Perhaps, the situation is now different with Vista, because it has more gimmicks than any other OS. I didn’t try the tweaking tips on SpeedyVista, though. The real value of this site, however, is the list of Vista services with its explanations. This is compulsory reading for any Windows admin.