Somethings I have been growing in a green house that are easy and quick:
Corriander (cilantro)
Round Carrots (these are great!! bought them from pampered piggies)
Dandelion
Cos lettuce (yup, its so easy to grow, but now I am over run with cos seedlings
the seedlings grow within about a week and a half)
Timothy Grass
Orchard Grass
Parsley
Mint
Capsicum/bell peppers
Just to name a few!
PS. If you plant cos lettuce, unless you have a huge place to put them only plant on maximum 25 seeds haha.