It adds statistical windows to the town, train and road vehicle dialogs, so you can monitor for example the growth of population, or the decrease in value of trains. It's only minor, but usefull I think.
Please give comments. Note that this 'project' is mainly to increase my C programming skills...

r2 [2005-08-29]:
-Fixed window bugs
-Added statistics for road vehicles
-Now in .patch file
-Should work with OTTD r2900
Known bugs:
-Closing vehicle main window doesn't close statistics window
-Train value incorrect