Formal:
* Discourse: A formal and extended discussion or presentation of a topic.
* Treatise: A written work that systematically examines a subject in detail.
* Monologue: A long speech by one person, especially in a play.
* Harangue: A long, aggressive speech.
* Diatribe: A bitter and abusive speech.
* Oration: A formal, prepared speech.
Informal:
* Rhapsody: An enthusiastic and effusive expression of feeling or admiration.
* Ranting: A loud, incoherent, and often angry speech.
* Outpouring: A spontaneous and heartfelt expression of emotions.
* Rambling: A long and unfocused speech or writing.
* Soliloquy: A long speech in a play in which a character alone on stage expresses their thoughts.
* Confession: A lengthy admission of wrongdoing or feelings.
The specific term you choose will depend on the context, tone, and purpose of the effusion.