Dudu Shmaya has just released a plugin for Cropper to create TFS work items from screen captures. You can also use it to add screen capture attachments to existing work items. We already use both Cropper and TFS, and this new plugin should be very useful for creating bug reports.
Dudu says he plans to submit the source code for his plugin to the CodePlex project for Cropper plugins soon. Looks like there are some other nice plugins already on their too.