In US ships I've seen many naming conventions used. Though contrary to what you suggest probably more likely to be named for a place then a person. However, many other countries name ships for people as well. At least I've seen Russian and Brits do it.
About naming after people in the US though:
In small shipping companies, especially tugboats, it's usually the name of a family member: Ex: Margaret Moran, Brendan Turecamo,
Next are ships named for a benefactor, or someone important in securing the funding or making sure the project gets completed. Ex: USTS Kennedy, USS Jeannette(formerly HMS Pandora)
Finally, ships of the same class or line all named after a group of people in memoriam. Ex: APL's president named ships of the '40-70s, and Liberty Ships such as the SS JOHN W. BROWN and the SS JEREMIAH O'BRIEN