Lifehacker discusses hotlinking, and recommends:

"Web site ImgRed (Image Redirection) lets you quickly embed an image from another web site and embed it elsewhere without leeching bandwidth from the source. Just grab the URL of the image and append it to http://imgred.com/ (e.g., http://imgred.com/http://example.com/pic.jpg). The site copies the image to their server the first time it's requested, then serves it up permanently. Handy."


http://lifehacker.com/software/web-publishing/quickly-embed-an-image-without-hotlinking-250290.php