Well, as always we need to keep up-to-date with the multitude of studies out there. I've just been revisiting the iron issue in regard to spinach/kale, etc. and oxalate. Here's what I've found:
Oxalic acid binds with the calcium in the food itself and reduces the bioavailability of the calcium in the food, but it does not reduce the body's ability to absorb calcium of other foods eaten at the same meal.
As for iron, NEW study and older ones now surfacing have OK'd oxalic acid. (I have to change my info sheet on iron.) Unfortunately the non-vegan websites have not updated their information!
This is a main stream government website quoting a scientific journal.
jn.nutrition.org/cgi/reprint/110/8/1618.pdf (may have to copy and paste this link to your address bar)
Here are a few sites with info:
http://en.wikipedia.org/wiki/Spinach Scroll down for this quote: "Spinach also has a high calcium content. However, the oxalate content in spinach also binds with calcium, decreasing its absorption. Calcium and zinc also limit iron absorption. The calcium in spinach is the least bioavailable of calcium sources. By way of comparison, the body can absorb about half of the calcium present in broccoli, yet only around 5% of the calcium in spinach. Oxalate is one of a number of factors that can contribute to gout and kidney stones."
So you can see there are still a few minor issues with oxalate, but nothing that should keep you from eating your spinach!