Is it possible to change the theme of the mouse cursor some how? I would really like to use this x11 mouse cursor theme:
http://www.gnome-look.org/content/show.php?content=27913

Nobody?

There is a product to do this, but it has not yet been released as an Intel compatible app:

http://www.unsanity.com/haxies/mightymouse

Actually this PPC MightyMouse app still works on intel os x - provided you've got a unibin Application Enhancer installed. You can load a cursor scheme manually from terminal.

Please provide the detailed installation instructions, L_X..
a link or something would also be nice

OK, download and install Application Enhancer and Mighty Mouse from http://www.unsanity.com/

open terminal and type ~/Library/PreferencePanes/Mighty\ Mouse.prefPane/Contents/Resources/MightyMouseCursorInstaller <path of mightymouse theme file>
(or the same without "~" if you chose to install mighty mouse for all users)

the cursor themes can be found at http://rampant-mac.com/resexcellence/index.html
however the site seems to be down at the moment. Mighty mouse provides a few sample cursor themes though.