(I don\'t want to hear about how crazy I am to want that! :)
Focus-follows-mouse is also known as point-to-focus, pointer focus, and (in some implementations) sloppy
Codetek had a product that did this but they never released a version for Leopard or later.
MondoMouse can sort of do focus-follows-mouse, but not auto-raise. Even the focus-follows-mouse is broken though. For example, it doesn't play well with command-tab (if you command-tab to a new application and don't touch the mouse then it should not switch focus back to wherever the mouse pointer happens to be -- I'm pretty sure every implementation in Linux I've seen gets this right but MondoMouse doesn't).
You can enable focus-follows-mouse (no autoraise) for just Terminal windows (just execute the following in a terminal):
defaults write com.apple.Terminal FocusFollowsMouse -string YES
And similarly for X11 windows:
defaults write org.x.X11 wm_ffm -bool true
(For mac versions previous to 10.5.5 this was:
defaults write com.apple.x11 wm_ffm true
)
I don't know of any other applications that support it.