It depends. A school that is mostly online and for-profit like University of Phoenix would probably not be looked at favorably by a portion of potential employers. However, there have been many people who have received these degrees that were accepted.
I recommend that you avoid the for-profit schools because of cost. Schools like University of Phoenix overcharge by large amounts. I believe the current tuition at UoP for graduate coursework is close to $800 per semester credit hour. Why would you pay that if graduate coursework at a state university is only $300 to $500 per semester credit hour?
There are plenty of programs at state universities. You just have to look for them. The best place to start looking is at your state university. If I knew what state you were in, I could provide you a direct link to the distance education program at a university in your state. However, here are some other schools to get you started.
http://www.fhsu.edu/virtualcollege/
http://www.peru.edu/offuttafb/degreeprograms/onlinelearning.htm
http://outreach.uwyo.edu/ocp/
http://www.distance.msstate.edu/
http://www.distancelearning.ufl.edu/degrees.aspx
http://www.apu.apus.edu/index.htm
http://www.online.uillinois.edu/
http://www.depts.ttu.edu/ode/CollegeOverview.asp
There is a forum with people who have received their degrees by attending online. http://forums.degreeinfo.com The forum is free to join, but if you just want to read posts, you don't have to join.
Good luck,