Broccoli, Coliflower, Brussel Sprouts, Cabbage, Peas, Lettuce.......Any early cool crops you plant in the spring and harvest in early summer...
I already have my Cabbage and Broccoli in....now is the time to plant them.....the sooner the better!
If you get well established Cucumber plants (transplants in containers), there is still enough time to get a last crop out of them!