Dave, you will want to consider adapting the open educational resources from Bridge To Success, http://bridge2success.aacc.edu/about/.

You might also look at the free extracts from Open University UK courses, e.g., Numbers, Units and Arithmetic, http://www.open.edu/openlearn/education/mathematics-education/numbers-units-and-arithmetic/content-section-0, or the Preparatory Course structure offered by Open Universities Australia, e.g., http://www.open.edu.au/courses/preparatory/uniready-enabling-units/ (not OER, alas).