Add link to django REST marshmallow

docs/api-guide/serializers.md

@@ -1022,6 +1022,10 @@ A new interface for controlling this behavior is currently planned for REST fram
 
 The following third party packages are also available.
 
+## Django REST marshmallow
+
+The [django-rest-marshmallow][django-rest-marshmallow] package provides an alternative implementation for serializers, using the python [marshmallow][marshmallow] library. It exposes the same API as the REST framework serializers, and can be used as a drop-in replacement in some use-cases.
+
 ## MongoengineModelSerializer
 
 The [django-rest-framework-mongoengine][mongoengine] package provides a `MongoEngineModelSerializer` serializer class that supports using MongoDB as the storage layer for Django REST framework.
@@ -1038,6 +1042,8 @@ The [django-rest-framework-hstore][django-rest-framework-hstore] package provide
 [relations]: relations.md
 [model-managers]: https://docs.djangoproject.com/en/dev/topics/db/managers/
 [encapsulation-blogpost]: http://www.dabapps.com/blog/django-models-and-encapsulation/
+[django-rest-marshmallow]: http://tomchristie.github.io/django-rest-marshmallow/
+[marshmallow]: https://marshmallow.readthedocs.org/en/latest/
 [mongoengine]: https://github.com/umutbozkurt/django-rest-framework-mongoengine
 [django-rest-framework-gis]: https://github.com/djangonauts/django-rest-framework-gis
 [django-rest-framework-hstore]: https://github.com/djangonauts/django-rest-framework-hstore