WGU is fully accredited, same accreditation as a state university. It is completely self-paced, there are no classes- just suggested reading and references to self-teach. You simply test for each subject's final exam whenever you are ready to do so. Testing is stringent, and is done in proctored centers (usually a local state or community college testing center).
You pay by the semester, and if you test out 4 years in that one semester, you are done- here is your diploma. I did it, transferred my associates from a military school and dove in. 2 semesters later, I had a BS:Information technology to hang on the boss' forehead. Could have done it in one semester, but I burned out/got lazy at the end and went long. With things like OpenCourseware, KhanAcademy, and similar for resources, you can learn any topic.
Link:http://www.wgu.edu/