General:
* States
* Declares
* Indicates
* Explains
* Relates
* Mentions
* Reports
* Notes
* Observes
* Remarks
Informal:
* Says
* Speaks
* Talks
* Writes
* Reveals
* Whispers
* Shouts
* Mumbles
Formal:
* Pronounces
* Affirms
* Asserts
* Avers
* Proclaims
* Maintains
* Contends
* Argues
Specific to a particular source:
* According to...
* As per...
* In the words of...
Figurative:
* Whispers
* Cries out
* Boasts
* Rants
* Hisses
The best synonym will depend on the specific context of your sentence.