I got my Mac Mini at the office last week. It came w/a standard mouse, not the Mighty Mouse. Since I'm addicted to the scroll wheel, I replaced it with a Microsoft Wheel Mouse I had laying around (yes, blasphemy!). The mouse works great but one thing that the drivers for OS X don't give you that the Windows drivers do is a setting on either scrolling one screen at a time or X lines at a time. Since I spend most of my day in Thunderbird and Firefox this was annoying. Even worse, I found that in Thunderbird it caused me to skip over messages in my Inbox folder when I scrolled through it so I “found” some emails.
Anywhoo, here's the fix: In your Thunderbird and Firefox prefs, set mousewheel.withnokey.action to 1 instead of zero. That tells those apps to scroll one screen at a time.