Quick object recognition: YOLOv3
Three common application to images are image classification (Is this an image of a cat or a dog?), image segmentation (Which part of this image (=which pixels) is/are dog?) and object recognition (Is there a dog in this picture? How many? Where are they?
Object recognition in images has become tremendously good, and you can have a modern network up and running in no time. A fun afternoon project is running the YOLOv3 (You Only Look Once) network on your webcam feed, and then think about what problem you could solve using these detections.
The author has a great tutorial here: