I've made some phone calls and done some more looking around online.
Regarding some of the organizations suggested previously:
America's Second Harvest is responding directly to Midwest flooding. There are people already 'on the ground' in the affected states, but I couldn't get answers regarding giving directly to that cause through ASH - because the staff was in a meeting about the floods when I called. :) The phone rep I spoke to was pretty sure that directed donations would be accepted, but didn't want to mislead, so I will be calling back about that to confirm. Only 2% of donations goes to admin and overhead, so 98% of all donations go directly toward relief. That's a very good ratio.
Mercy Corps tends to work toward international relief, not within the USA. There are some exceptions, though not Midwest flooding at this time. If this should change in the future, it would be reflected on their web site.
Habitat for Humanity has no programs specifically directed toward Midwest flooding at this time, though that is expected to change in the future. I was referred to their disaster response team for further details but unfortunately the representative was unavailable when I called. I'm going to call back tomorrow.
The Hunger Site (GreaterGood.org/CharityUSA.com) does have options for donations at their store. The option is to give in $25.00 increments and according to the phone rep I spoke to, 100% of the donation goes toward relief. If the following links don't work, go to The Hunger Site store
http://shop.thehungersite.com/store/site.do?siteId=220and search for "midwest flood" to see the listings.
Help Flood Victims in the Midwest
https://shop.thehungersite.com/store/item.do?itemId=33557&siteId=220Help Animal Victims of the Midwest Flood
https://shop.theanimalrescuesite.com/store/item.do?siteId=310&itemId=32999Most helpful online pages with further charity listings:
Charity Navigator: Helping Victims of the Midwest Floods
http://blog.charitynavigator.org/2008/06/helping-victims-of-midwest-floods.htmlTHE MIDWEST FLOODING; How to Donate To Flood Relief
http://query.nytimes.com/gst/fullpage.html?res=9F0CE2D8153DF937A25754C0A965958260HTH!