How to increase "tracking speed" beyond the maximum?

BetterTouchTool does that, and lets you add application specific gestures as well!

In BetterTouchTool, open Preferences. In the left bar under Advanced Settings choose either Trackpad or Magic Mouse. There is a slider that adjusts the tracking speed.

I don't think I could use a mac without it, at this point. I have my browser-tab-management and finder shortcuts mapped to multitouch gestures.

The value of the preference is stored in ~/Library/Preferences/.GlobalPreferences.plist and can be changed with something like defaults write -g com.apple.trackpad.scaling -float 5.0. The normal maximum value is currently 3.0. Applying the changes requires logging out and back in.

For those who come here searching for mouse speed up (as me), change the command/property mentioned on the answer of @user495470 to com.apple.mouse.scaling.

So:

defaults write -g com.apple.mouse.scaling -float 5.0

is what you're looking for.

Here is @Kodos Johnson :)

Mouse Curves is a preference pane that allows you to customize the tracking speed of the mouse and trackpad.

http://triq.net/mac/mouse-acceleration-preference-pane-mac-os-x