Two good online sources that I have used are:

Louisiana State University

http://www.is.lsu.edu/

Brigham Young University

http://ce.byu.edu/is/site/

the courses aren’t easy but they are relatively inexpensive and the material is well taught. Both are well enough respected that transfer is not usually an issue.

If you want to try some of the finest education in the country and have a little money to spend on it:

Harvard Extension

http://www.extension.harvard.edu/DistanceEd/

English E-129 on Shakespeare’s later plays. 4 credits only $700

Some other very well respected courses online include UMass, Florida State, UCLA, UNC-Chapel Hill, and almost every state university in the country. 🙂