Menu > Admin > System Setup > Contact Management > Define Source
This allows you to run reports of Leads and Companies by where they originated from to being added to your contact list.
Click to add Source.
The source is ultimately seen as being connected to a Company record. You are able to select a Source via a Lead record: Company Info area or from the Company record: Company Info area.
After defining the Source, you are able to use this field for reporting and grouping of records in the listing screens and reports associated with Leads, Contacts, Companies, and Opportunities. The available field is "Company Source".