Britney Spears and Justin Timberlake together back in the day.  How times change.  Now? The closest they come together is on this week's Music Power Rankings chart.

Only a few years ago, she was a train wreck. Now Britney Spears is an unstoppable locomotive. Tuesday night’s Spears’-themed “Glee” episode was the highest-rated episode in the show’s history among 18-49 year olds. The cast-version of “Toxic” soars up the iTunes chart, as does the six-pack of tunes from the show.

1. Britney Spears (not ranked last week):  Oh Brit, Brit: We’re a Slave 4 U.

2. Zac Brown Band (not ranked): With a little help from pals Alan Jackson and Jimmy Buffett, ZBB’s second Atlantic album, “You Get What You Give,” comes in at No. 1 on both the Billboard 200 and Top Country Albums, besting Maroon 5. Chicken Fried? We say Platinum Fried.

3. Lil Wayne (not ranked):  In what may be the most prolific stint ever behind bars for any inmate in the history of incarceration, Weezy released a new album on Monday and began promoting the “Def Jam Rapstar” video game, which it out Oct. 5--a month before Lil Wayne is.

4. Eminem (not ranked): With “Recovery’s” sales of 64,000 this week, the album surpasses Lady Antebellum’s “Need You Now” as this year’s top-selling album. Let the hair-pulling and cat-fighting begin.

5. Neil Diamond (not ranked): After years of his fans justifiably griping, Diamond makes the cut for the 15 nominees for induction into the 2011 Rock & Roll Hall of Fame. We predict definite inclusion for this Solitary Man.

6. Mulve (not ranked): Despite the RIAA’s efforts to close it down, citing the Digital Copyright Millennium Act, this free download service resurfaces with a database of 10 million tracks. We give it through the weekend.

7. My Chemical Romance (not ranked): Dramatic rock band returns after four-year absence as first single “Na Na Na (add 1000 Na’s) and promptly goes to the head of the class as  the song is the most-added track at alternative radio and lands at No. 1 on iTunes Alternative Songs chart.

8. Justin Timberlake (not ranked): He stars in “The Social Network,” which opens Oct. 1, his “SNL” appearance answers the question about when we’re getting new music (not anytime soon) and he’s got a video viral sensation on his hands with his History of Rap with Jimmy Fallon and The Roots. Are we looking at an EGOT contender? Can he get it before “30 Rock’s” Tracy Jordan?

9. Vevo (No. 4): The Universal Music Group/Sony-owned music video service keeps coming on strong. Last week came word that the web site may expand to television and now its Comscore score for August lands it in the top five with 45.4 million unique viewers. That ranks Vevo below YouTube but above Fox, NBC Universal and, prime rival Viacom Digital (that would include mtv.com, vh1.com and cmt.com).

10. Katy Perry (not ranked): She ends up having the last laugh after “Sesame Street” yanks her “Hot N’ Cold” segment, declaring it is too hot. She makes light of the situation on “SNL” as “The Simpsons” decide she’s just right for their show.

Music Power Rankings appears every Friday.  What do you think of this week's rankings?  Share your thoughts below.

Last week's power rankings