Clustering MySQL with InnoDB engine
Moving to Galera would be an option. Then your application has to be aware of 'deadlock detected try restarting transaction' errors. 
Another possibility is to set up a read slave and configure your application to use this slave for read_only queries. If one slave isn't enough you can add more and use them with a loadbalancer of any kind. Examples are maxScale, ha-proxy on application layer or ipvs on transport layer.