The Story of Ruth is another Old Testament Film that I have never seen. It is also quite surprising that although there have been numerous films about Esther this is the only feature length film that I am aware of that is directly about Ruth. There is half hour claymation film Ruth (right) from the 1994 "Testament" series. This series covered nine biblical stories in a range of different animation styles from plasticine / claymation through to more traditional hand drawn animation. It was a collaboration between Russian and Welsh animators. The other entries in the series were: Creation/The Flood, Abraham, Joseph, Moses, David and Saul, Elijah, Daniel, and Jonah. All 9 were fairly standard re-tellings of the story, which never captured much excitement. That said the animation was superb and in many cases, particularly Ruth the result was quite moving.
The only other film I know of which has examined this material is Amos Gitai's 1992 film Golem, l'esprit de l'exil (Golem, Spirit of the Exile) which makes the story into a modern day allegory about the Jewish mythical creature who personifies exile, with Ruth, Orpah and Naomi living in 1990s Paris. I'm only familiar with Gitai's Esther, but I've found a brief review of the film, and a pre-beard Peter Chattaway briefly mentions both Ruth films at the end of this page at Canadian Christianity and discusses it a bit more here.
UPDATE: Another film about Ruth is the 1958 films Ruth: A Faithful Woman which I've now reviewed