The Back Table was and is a social group at Grinnell College generally consisting of people who, even in a college as liberal as Grinnell, were and are considered outcasts. The joke went that Grinnell is a college of non-conformists... all not conforming in exactly the same way. Except the Back Table, or, as some still call it, the Bat Table. (That's a long story, for another time.)
As I understand it, it started sometime in the late 1980s or early 1990s when certain members of the soon-to-be-formed social group insisted on sitting at a corner table during meals because the people in question preferred to eat with their back to the wall. The group eventually moved from North Campus to taking its meals in the Quad dining hall on South Campus, which is where most people think of the Back Table or "Freak Table" being "headquartered".
To get a sense of the sort of people who hung out at, and still hang out at that particular table every meal at Quad, from around 1993-1995 the joke was that everyone at the table was a polyamorous bisexual pagan. This was not, and is not strictly true. By definition, the Back Table is and was full of exceptions. But it is true that most members of the Back Table were at least three of the following:
polyamorous * bisexual * pagan * gamer * sci-fi geek * mathematician * queer * salt-eating * insane * linguist * juggler * liberal * anarchist * transsexual * computer nerd * cat-lover * X-phile * otaku * hippy * alien * hacker * SCA enthusiast * artist * lover * hat-collector * foreign national * history buff * fnord * silly
The Back Table still exists today, making it at least a decade old, having spawned BBSes, majordomo mailing lists, and Web sites. Perhaps this says something for those who take the road less traveled, and write silly poetry while they do it.