Commission is always negotiable, and the Department of Justice even condones it as good competitive behavior among agents.
The typical commission is close to 6%, but that can really vary depending on the location and price of the home you're wanting to sell. Many agents are willing to be flexible on commission rates, but it's not something they like to advertise. And most clients are not very capable or comfortable negotiating rates.
At UpNest, http://www.upnest.com, we created an online marketplace where home sellers can confidentially submit their homes, and multiple top local agents will compete to obtain your listing. Some agents lower their commission rates to stand out, and every agent that submits a proposal is an experienced agent, so it's not the same as working with a low grade discount brokerage.
Hope that helps!