Invest in a graduate schools book. Plenty of schools take people for certain programs with a 2.7+ and probably one or two take people with a 2.5 +. Below this, I'd think about retaking some courses you didn't do very well in. Where there is a will, there is a way. Historically, I have found it helpful to contact someone in a program you are interested in, tell them your situation, and let them tell you what you have to do to have a good shot at their program.
I concur with SugarNaCl, my masters program only required a 3.0 in the last half of your undergrad studies, which may not equate to a 3.0 overall. Even if you do not gain admission to the full program, most grad schools offer conditional acceptance to which you must maintain above a certain GPA for your first few classes to no longer have the provisional status (usually B and higher in each course).
I had barely above a 3.0 and got into a masters program, unconditionally, as well as admitted to a certificate program at a medical school. I chose the masters because of the real degree vs. certificate.