You'll have to wait until April before Battlestar Galactica airs in the US, but in the meantime check out this comprehensive preview on YouTube courtesy of the Canadian TV show HypaSpace.

You can also watch a short but intriguing teaser trailer here, with shadows crossing the faces of the major characters as each face blends in with the next.

There's a longer official Battlestar Galactica Season 4 trailer here too.

The plot for the fourth and final season will apparently revolve around finding earth, revealing the last of the "final five" Cylons, and tying up loose ends regarding Starbuck and Baltar.

When asked whether it had been decided who the fifth Cylon would be, Ronald D. Moore, Battlestar Galactica's executive producer, said “It’s definitely been decided who that one is.” He added, “I can’t say when, but we’re certainly not waiting until the last episode to tell you who it is."

Here's a video showing the cast and crew discussing Battlestar's final season at a press conference in August 2007.

Will they reach Earth? Is Starbuck a Cylon? And what about the Gyus Baltar Cylon connection? Is he dreaming No. 6, has he gone mad, or is there something else going on?

Let's hope they take it out with a bang and continue the intriguing political sub-text, the excellent writing, along with the outstanding special effects and acting that have made Battlestar one of the most engaging science fiction television spectacles in recent years.

I'm keen to see how they tie up the religious themes from the first three seasons that appear to revolve around Baltar and his invisible Cylon companion, the baby human/cylon hybrid, and Starbuck's ultimate destiny.

The first of 20 episodes of Battlestar Galactica's fourth season titled "He that believeth in me" will be broadcast in early April on the Sci-Fi Channel in the US. The Sci-Fi Channel hasn't decided if the final season will all air this year or will be spread over 2008 and 2009.

Be sure to watch the prequel to the fourth season titled Battlestar Razor, a two-hour episode that adds more background material to the show's cylon/human mythology. You can watch a trailer for Razor on YouTube here. There are also a series of Razor Flashbacks, 2 minutes episodes first published on the web and then later on the Sci-Fi Channel, some but not all of which form part of the two hour Razor special.

"The two-minute segments tell the story of young William "Husker" Adama’s rookie Viper mission during the first Cylon war," according to the Sci-Fi Channel's website. "In addition to fighting for his very survival against relentless Cylon centurions, Adama makes a terrifying discovery that will come back 40 years later to threaten him, the crew of the Pegasus, and the survival of the human race.”

You can watch all seven two minute Razor Flashbacks in one video here.