ThingLink is a site that allows you to make your images interactive by adding little interactive "hotspots" to it. These "hotspots" can link to a website, video, audio, or text. Here is an example:
ThingLink is free, but you are limited to 10 image uploads and 100,000 views. Thanks to Nancy Sharoff, who shared this resource on the Discovery Education Blogs, you can get an educator's discount and sign up for a year for just $20. This will give you Plus account with the ability to upload 500 images with 500,000 views. Use coupon code TLEDU for this special pricing.