RABBAN YOHANAH BEN ZAKKAI is the subject of a post-Ninth of Av meditation by Rabbi Reuven Hammer in the Jerusalem Post. Excerpt:

As with so many ancient tales, we may never know exactly what happened, but the general story is clear. He escaped from Jerusalem, made contact with the Romans and was given permission to reside in Yavne together with "its Sages." Some speculate that other Sages had been kept in detention in Yavne, others that it was simply a center for study. Whatever the case, Yavne then became a center for the preservation of Jewish tradition and the Sages were able to lead the nation when all political frameworks had been destroyed.

UPDATE (14 August): A while ago Carl Kinbar e-mailed:

Regarding the subject of R. Hammer's article in the Jerusalem Post, may I refer you to an article in the Jewish Studies Internet Journal, vol.4, "Yohanan ben Zakkai, Amicus Caesaris: A Jewish Hero in Rabbinic Eyes" by Avram Tropper at http://www.biu.ac.il/JS/JSIJ/ca.htm. Tropper parses the various attitudes toward Yohanan that appear in the early sources.

JSIJ is a fine example of an open access, electronic peer-reviewed journal. In my estimation, it is unsurpassed in the broader field of Jewish Studies journals and a hopeful sign for OA in the humanities.

I noted the article some time ago, but it's helpful to note it again in this context.