I am concerned about my undergraduate GPA, I got 3.0 out of 4.0. I will be applying for MBA programs in the USA starting in 2017, when I will have about 3.5 years of work experience.

There's no way to go back and re do classes, but is there anything else I can do to make sure I get into the best program possible? Are there business schools that have lower GPA requirements that I should look at?

You could also take a for-credit course part-time or online and get a higher GPA. A high GMAT will also help balance a low GPA.

Good fodder for a low GPA includes anything that shows your aptitude to apply yourself academically. A higher than average GMAT score would certainly help. Depending on the circumstances, you may feel you need to explain what happened in your personal statements.

If I take free online classes on Coursera or another provider, would that help? Unfortunately I do not have the time to take any for credit courses.

That would not help because there would be no grade.