I dread crate rest and long recovery periods for my hounds. Especially with sporty greyhounds, someone is always bound to get hurt and it can be very difficult to convince an abnormally active greyhound to be inactive. I do my best to provide entertainment and stimulation for my greyhound patients and try to minimize boredom. Here are a few ideas:
Sunning. Reagan especially loves to sun. 90 degrees out and she loves the sun beating down on her. As long as we are dealing with an injury (not an illness), I like for my greyhound patient to heat up and even start panting for a few minutes. Panting and having to cool down will burn a little energy. Of course, Reagan is one of the few greyhounds that handles the heat really well. She rarely pants.
Kongs. I love Kongs. I probably have 20 Kongs. A very easy Kong stuffing is to fill the Kong with kibble and then use a knife to mix in canned pumpkin, creme cheese, canned dog food, or peanut butter. For kibble eaters, I will stuff entire meals into several Kongs and turn that 30 second meal into 30 minutes of entertainment. If your dog is very food motivated or has Kong experience, pack it tight and freeze it. For Reagan, I am stuffing her Kongs with chunks of meat I am cutting off of the turkey necks, beef, rice, veggie mix, and the offal of the day.
Grooming. If your hound has hair, its a good time to get the Furminator or the grooming mitt out. With Reagan, I just go over her coat with a soft brush (I don't want to lose any more of it).
Massage. Massage is a great way to calm and relax your hound. Some people constantly touch their dogs mindlessly. Massage is a great way to make you step back and pay attention to what you are doing and to find out what your dog actually likes. Katie loves for the loose skin around her neck to be massaged.
Depending on the injury, clicker training might be an option. For example, Travis stepped on glass and it had to be surgically removed. He was bandaged, sore, and wasn't ready to run yet, but I kept him busy by teaching him to play dead. 
Reagan and I have been working on sit stays, dumbbell holds, and have started some preliminary scent article work since she can do all of these from a stationary position.
Entertaining the injured can be tricky, but it is worth the effort to keep the canine patient happy.
