UPDATED: Re-Add Selected Tracks as Podcast v1.2
Re-Add Selected Tracks as Podcast will re-add the files of the selected tracks to iTunes as if they were a Podcast subscription. The files will then appear in the Podcasts playlist and "behave" as though they are a group of Podcast episodes. Requires Web Sharing be activated.
This newest version is compatible with iTunes 7.7.1.
Also, I should note that there is a known Leopard/Apache bug that may prevent Web Sharing from working correctly. Many users facing this problem have had success using information from this Apple discussions link and item 5 from this macosxhints forums link. I do not know the status of this bug other than what I have read in the posts cited above.