General synonyms:
* Agreeable
* Amiable
* Accommodating
* Obsequious (slightly negative connotation)
* Submissive (can be negative)
* Yielding
* Tractable
* Amenable
* Pliable
* Deferential
More specific synonyms:
* Courteous: polite and respectful
* Easygoing: relaxed and tolerant
* Obliging: willing to help
* Suave: smoothly agreeable and sophisticated
* Servile: excessively eager to please (negative connotation)
The best synonym will depend on the specific context in which you are using the word.