Many themes require posts with a featured image selected, but many of us have old blogs without that image. The new plugin “Satollo Thumbnails” not only provides an automatic filter to simulate the featured image for every post missing it, it add a real thumbnail generation with an integrated cache.
This way, themes which request a thumbnail to WordPress will get back an image exactly of the requested dimensions, optimized and cached.
Read more about Satollo Thumbnails.