Microsoft Photo Info is a free software application that
allows photographers to add, change and delete common “metadata” [EXIF] properties for digital photographs from inside Windows Explorer. It also provides enhanced “hover tips” and additional sort properties for digital photographs in Explorer (in Details view).
I found it quite useful, and you can’t beat the price: free! However, in order to download it, you have to go through Microsoft’s draconian Windows verification process, which seems to only work through Internet Explorer. :-p