We automate the versioning with subversion, ccnet and nant.
Our script parses the folder path( /Branches/1.4.5/Source...) and extracts the version number (1.4.5). After that we retrieve the current revision number from subversion and we place it in the last position of the version (i.e. 1.4.5.346). Once we have the complete version number we inject it into all the assemblies and write it to a version.txt files so it easy to determine what version is currently deployed on the web servers.