I have tested several programs that can be used to search for videos on Youtube, download them afterwards and convert them to another format. The portal iDesktop offers all those functions plus the option to play Youtube videos on their website in a very nice interface. Users can perform searches for Youtube videos which are displayed as thumbnails with titles. The size of the thumbnails can be changed on the fly which means that it is possible to fit a lot (55 in my case) of videos on one search result page. The biggest size displays only three per page.
