Display post thumbnails for post summaries in Blogger

I've seen blogs which display post thumbnails with its post summary in their homepage, search results, label results -- well as long as it isn't a static page or the post page itself. You can do this in a number of ways. You can settle for thumbnail images at the beginning of your posts, or create two versions of your post image (a thumbnail size and its original size) or perhaps use a script to do the resizing.