YouTube HD Transfer
It's a tabbed based program that can be used to download single YouTube urls that are pasted into the program or to batch download many videos at once. It includes a preview function to preview the videos before downloading them and an easy search function.
The search provides access to several filters to return specific results. Those filters include duration, upload date and category filters, returning only high definition videos, searching for the exact phrase. Sort options are also provided in the search interface.
Note: YouTube HD Transfer requires Internet Explorer 7 or higher to be installed.