Eric Meyers has a nice article about the earliest synagogues in The Jewish Week. He is especially interested in the immediate post-70 situation and what it might tell us about the development of Judaism:
One of the more important and sensitive historical issues that has emerged in the course of this debate, based to a large degree on the paucity of synagogue remains post-70, is the degree to which classical Judaism arose in response to Christianity or the degree to which the tragedy of the two wars with Rome (66-70, 132-135 CE) led the Jewish people to re-evaluate their tradition and successfully reinterpret it within the changed circumstances of two crushing defeats.
In my view this period in the history of Judaism was as definitive as the period after the destruction of the First Temple in 586 BCE when the exiled Judeans not only survived but managed to pray without the Temple and began the task of editing the books of Scripture that would help them maintain their identity and keep the traditions of former times. The first centuries after 70 CE also led to publication of the Mishnah by 200 CE and many of the early biblical commentaries. It is unimaginable that all of this literary creativity, along with the development of the synagogue liturgy, could have happened without a physical setting in which it could take shape. The most logical setting is the synagogue as a structure where the Torah was read, translated and interpreted; where homilies were given; and where the liturgy was sung and recited.