I think on-line education is the best way to get a degree if you're busy. I am currently studying for a masters in IT with the University of Liverpool and I find it amazing (www.ohecampus.com). Unlike what many think, studying on-line is very social, and interactive.
But online university is a great opportunity for some people.

You do have various options, but as you say, the cost issue is what will determine the final decision. Many online schools will work with you for financial aid, if that is a consideration for you, or check with your job to see whether they have a tuition reimbursement plan.
Go here - this site appears to have VERY complete listings/links.
http://www.college-scholarships.com
http://www.college-scholarships.com/ssac.htm