Battlestar Galactica

Battlestar Galactica (abbreviated to BSG) is a TV series about a group of humans trying to find a new home after their old one was destroyed by Cylons. Cylons are robots created by humans to act like slaves. As a result they rebelled and nuked humanity. Now the 40,000 or so people who managed to survive join up in a "ragtag fleet of ships". Led by William Adama, the commander of the Galactica, they try to discover Earth.

The Original Series
BSG originally aired in 1978. Its page on the Battlestar Wiki can be found here.

Galactica 1980
After the Original Series was canceled, BSG tried to make a comeback in 1980. Here is its page on Battlestar Wiki.

The Re-Imagined Series
This TV series aired in 2003. It is up to four seasons now, with the last half of the fourth season premiering in January 2009. Here is its page on Battlestar Wiki and here is its page on Wikipedia.

In Fanfiction
BSG has quite a pile of fanfic on The Pit, but there have not been any noteworthy Mary Sues to take note of.