Freedom isn’t free; it takes risk.

Last year’s inaugural Virgin Mobile FreeFest was a grand experiment, distilling the successful two-day, paid Virgin Mobile Festival at Pimlico into a one-day, free festival at the much smaller Merriweather Post Pavilion. The free fest hit on a hot new formula: It turns out giving away tickets really supercharges demand.

Last year’s festival co-opted Blink 182’s reunion tour with Weezer, and threw in a diverse range of hip-hop, indie and nostalgia acts. This year, Virgin flips the script, leaving the mainstream behind and returning with polarizing pop stars, reunited rock gods and a blockbuster indie dance group hanging it up in its prime. Tickets to this year’s fest again “freed out” almost instantly, and all signs point to another successful year.

You know who you’re dying to see. And even if you don’t have a ticket, you’ll find a way to get in. Here’s what you should expect — and wildly hope for — from Saturday’s 2010 Virgin Mobile FreeFest.

Most Unlikely Collaboration: Ludacris and Joan Jett
Do Ludacris and Joan Jett even know the other exists? They aren’t scheduled to play together, but we like to imagine that sparks will fly when they hear one another across a crowded festival field. Luda will embrace the snarl of “I Love Rock and Roll,” and an Aerosmith-Run D.M.C. moment for the new millennium will unfold before our very eyes. We also fully expect Thievery Corporation to lounge-ify Pavement’s instrumental “5-4=Unity” and for M.I.A. to hug it out with Jimmy Eat World. Could happen.

Most Likely to Induce Painful Nostalgia Attack: Pavement
Pavement may take third billing in the FreeFest lineup, but to anyone under 20 roaming around Merriweather Saturday, these indie guitar gods just look like someone’s dad. Jimmy Eat World provided these whippersnappers’ soundtrack to middle-school love and loss in the early 2000s. Pavement brings the rest of us back to the ’90s, when skateboarding through your angst about girls really meant something. Ten years after breaking up, Pavement is back, showered and laundered. And after a decade, Stephen Malkmus’ lyrics might finally resonate with those of us who were ankle-biters ourselves the first time around.

Most Potentially Puzzling Performance: M.I.A.
M.I.A.’s found herself embroiled in backlash since, well, always. But especially lately, around the release of “Maya,” her follow-up to 2007’s smash “Kala.” First she locked Twitter horns with a New York Times reporter, then a string of shows were marred by bad weather, bad sound and bad song choices. It’s up in the air whether M.I.A. will deliver the kind of transcendent headliner set she’s capable of or whether she’ll alienate yet another crowd.

Breakout: Edward Sharpe & the Magnetic Zeros
There are several young bands battling to break out at FreeFest, and of the four we think have the best shot, only Neon Indian hasn’t licensed a song for a car commercial yet. (They did, however, record a track for Mountain Dew’s record label.) And while we think the chillwave champions will deliver a perfect festival set, they have stiff competition in M.I.A.-endorsed noise duo Sleigh Bells, Coldplay wannabes Temper Trap — and, most notably, neo-hippie collective Edward Sharpe & the Magnetic Zeros. Sharpe’s been owning festivals all summer behind the ubiquitous “Home.” And rolling 10 band members deep, he wins with strength in numbers.

Don’t Miss: LCD Soundsystem
Yes, yes. We know this is likely Pavement’s only area show on its reunion tour, but this may be LCD Soundsystem’s last D.C. show. Ever. After three albums, James Murphy is hanging it up midstream. With a summer of killer festival sets behind him, Murphy has developed into quite the frontman, bringing epic dance anthems to the masses. There’s just nothing quite like hearing “All My Friends” live, so don’t spend it stuck at the beer tent.

Dance Forest
When we heard that FreeFest would feature a Dance Forest, our minds wandered into the woods of possibility. We dreamed we saw some mystical elves getting their groove on to Chromeo, Maximum Balloon, Modeselektor and other Dance Forest acts. May your own trip to the forest be mellow, and not at all spent chasing away imagined skeletons or dancing rainbow bears.

» Merriweather Post Pavilion, 10475 Little Patuxent Parkway, Columbia; Sat. 11 a.m.-10 p.m., pavilion seats $125; 410-715-5550.

Written by Express’ Rudi Greenberg and Shauna Miller
Illustrations by Ben Claassen

If you can’t make it to FreeFest, we’ve got you covered. Express’ Rudi Greenberg will tweeting from Merriweather throughout the day. Follow him @rudi_greenberg.