Northern Virginia Community College nvcc.edu has a 2 semester series, reasonably priced out of state. You may be too late to catch the summer semester, although sometimes they have staggered start dates or classes that are split into first 8 weeks and second 8 weeks.
I've never taken classes (but considered taking them) from Central Texas College. They have a long history of correspondence courses, now online classes, with the military. Cheap tuition and start dates every month. They do have a single class for the whole lifespan of Human Development.
As other places to check, try Colorado State University online.colostate.edu, Brigham Young is.byu.edu, American Public University apu.edu
Do you have specific schools you are applying to and are you sure they only require a 1 semester course? Several of the schools I looked at required 2 semesters.