According to the Live with Regis & Kelly website, Shannen Doherty will be a guest on their show next Friday, September 5th promoting the new series, 90210! Check your local listings for airings!

E! Online reports that Shannen and Jennie will have many scenes together and Shannen is currently signed on for a total of 4 episodes:

From E! Online:

That's what I'm hearing is in the cards for long-lost friends Brenda Walsh (Shannen Doherty) and Kelly Taylor (Jennie Garth) on the CW's new 90210.

According to reliable inside sources, producers are now planning plenty of ultracozy screen time for the two real-life frenemies—they'll even be shacking up together temporarily on the new series, which premieres Sept. 2.

"Jennie and Shannen will have many, many scenes together," said one insider about the four episodes for which Shannen is now contracted. (Jennie will appear in more episodes on a recurring basis.) [Spoilers can be found about Brenda's entrance into the show can be read here

According to Korbi @ Zap2It.com, Shannen and Jennie will reportedly have many scenes together and will be poking fun at their real-life rivalry. That should be interesting!

Is it really true that Tori Spelling is pulling out of 90210? Too sad!! -Char
Yeah, I guess the network and studio offered Shannen Doherty and Jennie Garth more cash per episode and Tori wasn't having it. However, if the show is a hit this Fall, things could turn around. We'll have to wait and see. In the meantime, we'll have plenty of Brenda-Kelly tension to keep us happy. I'm told that Doherty and Garth are down to make fun of their reported real-life rivalry, and they'll definitely have several fun scenes together. Scary how excited I am for this...

Sci-Fi has a press release regarding it's 2009 original movies and here it is:

SCI FI REVS UP MOVIE SLATE WITH SUNDAY ORIGINALS

Unprecedented 36 Original Movies Planned for 2009 To Air on Saturday and Sunday Evenings

Beverly Hills, CA - July 20, 2008 - SCI FI's original movie franchise promises more action, thrills, cataclysmic disasters and mythological adventures in 2009 with an unprecedented 36 original action movies - up from 2008's slate of 24. The Channel's high-octane, entertaining original movies have made SCI FI Saturday: The Most Dangerous Night of Television a destination for viewers, bringing in an average of 1.8 million viewers so far in 2008. In addition to the Saturday offerings, SCI FI will also present its original movie fare on Sunday evenings beginning next year.

SCI FI's original movie franchise is the Channel's homage to the classic popcorn feature, a re-imagination of cinema's most delectable sci-fi treats. Like the timeless fare that packed movie theaters and drive-ins, these non-stop thrill rides offer thoroughly modern escapist fun, running the gamut from traditional creature features to horror flicks and sleek, contemporary thrillers.

2009 Highlights include:

Lost Treasure of the Grand Canyon

A journey for a lost treasure leads to the discovery of an Aztec culture. Stars Shannen Doherty and Michael Shanks.

Source: The Futon Critic

Per USMagazine:

Tori Spelling is thrilled original 90210 member Shannen Doherty has been cast on CW's upcoming 90210 spin-off.

"It is going to be great," she told Usmagazine.com Saturday at the Much Love Animal Rescue's "Bow Wow WOW!" event in L.A. "The fans have been wanting this for a long time."

(Seems Spelling - who will also appear on the show down the line - has had a change of heart since penning her memoir, sTORI Telling. In it, she said Doherty "could be arrogant and carefree.")

Doherty will reprise her role as Brenda Walsh, who, after a successful theater career, has returned to West Beverly High as a guest director for the school’s musical production.

"She is a huge part [of the show]," Spelling said of Doherty. "Any original cast member is huge to the fans. She was there from the beginning. She was 90210. Shannen and Jason [Priestley] - they were the Walshes."

She also says her father, the late Aaron Spelling, would have approved of the spin-off.

"He would be really proud," she told Us. "He always intended to do a 90210 next generation. He would want his hands all over it."