Yes and no on that one - it is a good source but it is used a bit differently than animal based iron. With plant based iron such as in Spinach and other green foods one must also consume Vitamin C.

Believe me, when you have chronic Anemia (I have had it since I was a couple months along with Walker and still have it with him nearly 14 months old) I eat whatever I can with iron in it. I drink OJ with my prescription iron and that is still not enough. I eat steak 1-2 times a month just for the animal based iron.

But honestly, I love spinach and the vitamins in it are GOOD for you.

Example:
http://women.timesonline.co.uk/tol/life_and_style/women/diet_and_fitness/article7071479.ece

And PS: Every woman in child bearing years should be eating a good amount of folate naturally. Spinach is just awesome on that!