In our area there arent too many properties that make it too the tax foreclosure point. The main reason being that properties that get that far behind on their taxes usually have a significant mortgage as well. In which case the lender forecloses before the taxes have become that deliquent.
This doesnt mean they cant be found. One good resource for research is http://www.ioniacounty.org
then click on their online services, you can find tax info, look at tax maps etc.... You can also find who to call about tax sales as well.
Of course another great source is a local real estate agent, so feel free to call me as well.