well there is not a single company that gives cheapest rate to everyone...depending on age, driving history, gender and other factors each company gives different rates to each individual..

so the best way is to call or check online each company .. get a quote..and decide on the cheapest one...here are some companies to get started with

progressive, Geico, all state, esurance, 21st century, state farm, AIG and so many others

All the best !!!