Sloan-C report on online learning in US higher ed. Among the findings:

• 12% growth in the last year
• 20% of students took at least one online course in fall 2007
• Current economic problems (rising unemployment and fuel costs) are predicted to increase demand for online learning

According to a meta-analysis by the US Department of Education, face-to-face courses are less effective than online and blended learning. They caution against viewing this as simply a matter of the medium though. It's the changes in what online and blended learning allow (like opportunities for collaboration) that are likely making the difference.

Direct link to PDF: http://www2.ed.gov/rschstat/eval/tech/evidence-based-practices/finalreport.pdf