General:
* Welcomers
* Hosts
* Ambassadors
* Receptionists (if they have more responsibilities than just greeting)
* Concierges (in hotels)
* Doormen (for formal events)
* Usurers (in a more informal or humorous setting)
Specific to a particular industry:
* Customer Service Representatives (retail)
* Guest Services Agents (hotels)
* Event Staff (events)
* Front Desk Staff (businesses)
The best name will depend on the specific situation and the role of the person doing the greeting.