Ron Moore and co. are calling them episode 1.0 and episode 1.5. Each episode will still be an hour in length (including commercials).
As we've seen in the Web episodes, a resistance movement has begun on New Caprica. The leaders of the Resistance include Saul Tigh and Galen Tyrol. Admiral Adama and Lee Adama fled the Cylon invasion, taking the two battlestars with them. Most of the best Viper pilots were left behind on New Caprica. Adama vows to return to the planet to rescue the survivors despite the lack of key personnel aboard Galactica and Pegasus. D'Anna Biers takes on a larger role in Season Three, which promises to take an extended look at Cylon society.