Northern & Central Midwest
The Wildflower Information site is an excellent place to start looking for species to plant in your meadow. The site not only lists plants by region, but you can cross reference with scientific and common names. There is also information about native plants, invasive plants, and reference lists by soil and climate condition. This is a great place to start finding just the right mix of plants.
Making a Meadow
Pam Lewis, the author of Making a Wildflower Meadow (Frances Lincoln, 2006; $28.95), comes at the making of a meadow from a preservation point of view, providing good information about the specifics of meadow-making, especially the ecological connections that plants have with each other. It's possible to take from her information enough tips to create a small meadow garden outside the back door or several acres of meadow.