Here is an unknown spider I found apparently waiting for potential prey to come to a Maximillian sunflower. We have planted these Helianthus in a reconstructed "prairie" and they are quite spectacular at the moment.
Although this spider seems to be doing what crab spiders do (hunt in flowers by ambushing prey) and has the long front legs to grap prey with, it may not actually be a crab spider.
If anyone has found a good guide to common spiders please let me know the title and author. Spiders are always a problem to identify.