Last summer one of the members of our community garden shared with me his method for getting early spinach. He plants spinach in the late fall, lets it get started, and then allows it to be winter-killed. But, because it has roots established and spinach is quite cold hardy the plant will just bounce back in the spring with a head start on all the rest of the greens.
It didn't work perfectly for us--probably we started our spinach seeds too late when it was already starting to get cold as our germination rate was not very good. None the less we have six spinach plants that are way, way ahead of the rest which we planted this spring. I'll give it another go this year and see if we can have even better germination and regrowth rates.
I thought it was a pretty cool tip. Especially since we didn't even plant our spinach seed this spring until April. Its a good little jump start and puts us that much closer to our first crop of yummy, fresh spinach for the season.