I just discovered what appears to be free 90 day access to the CLEP and DANTES online tests of your choice through the Maryland Library system. Using my library card I simply go to Electronic Databases and there is a section for "Testing and Education Reference Center" - they have all kinds of test available - ranging from GRE's to special certification exams as well as CLEP and DANTES - it's amazing and it's free.

You only need a local library card from any of the counties in Maryland and you can get access.

I don't know if other State library systems will have the same but if you live in Maryland you won't have to pay for another test or hunt around for access through a local high school.