For some reason, Mac OS X 10.6 "Snow Leopard" removed font smoothing settings from the *Appearance* System Preference Pane. The new pane only has the option, "Use LCD font smoothing when available." Luckily, there is still a way to set font smoothing strength. Anti-aliasing on the Mac has always been too strong for my tastes, and I tend to use what used to be the "Standard" setting for my 30" displays and "Standard" or "Light" for my notebooks. In Snow Leopard, you can still set font smoothing by using the following terminal command:
defaults -currentHost write -globalDomain AppleFontSmoothing -int 1
I read on another website that the supported values are 1-4 for Standard, Light, Medium, and Strong, but I found that 0 was an acceptable value... and it seems to match "Standard", which would seem to suggest that supported values are actually 0-3.
Don't take my word for it. Here's are actual screenshots:
If that isn't obvious enough, you can [download a layered PSD file][psd] and toggle layers on and off to see the difference.