It may vary by state but yes, you and your friend can jointly own a car and can put each of your names on the title. The usual situation of course is when a couple jointly own a car and less frequently a parent and child will co-own a car. But there are plenty of situations on the net where someone is trying to get their ex-girlfriend or ex-boyfriend off their car title!
For example North Carolina recognizes joint tenancy on the car title.
New York's DMV specifically says that a vehicle can have two or more owners. Note that either owner can transfer ownership of the car without the other owner's permission in NY.
Some states may let you title a car but may not let you register it without proof of insurance. And I don't know how insurance companies treat sharing car insurance. Some may require that the additional driver live at the same address or be a blood relative if not living at the same address. Best check with an agent on that one.