SageThumbs is a powerful shell extension allowing to preview enormous amount of image formats directly in Windows Explorer by using Pierre-e Gougelet's GFL library (XnView's author). It is a free and open source image preview application that's straightforward.
Here are some screenshots to illustrate the features and user interface of this application:
USB Drive Letter Manager (USBDLM)
Icaros Shell Extensions
DVD Drive (icon) Repair
USB Manager
FileMenu Tools