Just a quick note to let the followers of GYBO know that I recently put together a table-style key to the sections of Carex and have posted it on my personal blog "The Vasculum". Feel free to travel there and get a copy for yourself.
Here's a pretty picture of Carex microdonta from Benton Co. Missouri to entice you.
The University of Wisconsin Extension Weed Science website has videos and information on how to identify various invasive plant species. To see this website and view the videos, visit http://fyi.uwex.edu/weedsci/category/videos/.