Formal:
* Commendation: A formal expression of approval or praise.
* Encomium: A formal expression of high praise.
* Laudatio: A formal speech of praise.
* Tribute: A gesture of respect or admiration.
Informal:
* Compliment: A polite expression of praise or admiration.
* Accolade: An award or expression of approval.
* Kudos: Praise or acclaim.
* Applause: An expression of approval, typically by clapping.
* Adulation: Excessive praise or admiration.
Other:
* Endorsement: A public declaration of support.
* Testimonial: A statement of praise, often written.
The best word to use will depend on the specific situation and the level of formality required.