Make a basic wooden frame, staple chicken wire over it. Place the wire frame at an angle on attached legs. You then use as a cucumber trellis and plant lettuce underneath! The cucumber vines won't strangle out anything else and the lettuce grows better with partial shade!!
Repurpose an umbrella as a greenhouse. Great idea.
Another great idea to start seeds! Make a greenhouse out of a plastic container like this spinach container. Cut toilet paper rolls and plant the seeds in them. Once the seeds grow into plants, you can just put the roll into the ground! Love this!