The best idea I found was these great books that go along with the Words Their Way Series.
You can also order them at Barnes and Noble and use your Teacher Discount if you want. I found the orange book on the shelves at Barnes and Noble but I had to order the red one.
There are other levels.......but these are the two recommended for kindergarten.
Another great idea which I will use is the spelling inventory.
Here is a link to a PDF I found of it online:
Right now I am still thinking how I want to incorporate this into my reading block of time. I am reading the book Daily Five to help me rethink how I am teaching reading.