Whose song will always remind us of the summer of 2008?

Everybody's got a personal playlist of summer songs. It might have Frank Sinatra's "Summer Wind," or Sly and the Family Stone's "Hot Fun in the Summertime." The Lovin' Spoonful's "Summer in the City," or maybe Regina Spektor's song of the same name. Seals and Croft's "Summer Breeze" might make you feel fine, though I'm betting the Isley Brothers' version would make you feel finer.

The 21 picks assembled here - on a playlist that can be burned onto one CD - are contenders for the songs of summer '08, tunes that may worm their way into your consciousness, if they haven't made it there already.

Some are already hits on radio, Internet or TV. One of them is 40 summers old - but thanks to McDonald's and its marketing plans for the Olympics, it will soon be inextricably linked with U.S. swimmer Michael Phelps and Happy Meals.

So, with apologies to the contenders that didn't make the cut - Los Campesinos!'s "You! Me! Dancing!", Missy Elliot's "Best, Best," and Dengue Fever's "Tiger Phone Card" - on to the list.

1. "Mercy," Duffy.

"Yeah, yeah, yeah!" Welshwoman Aimee Ann Duffy's calling card, off of her impressive debut Rockferry, is an international hit with good reason, as it sashays down the '60s soul-pop avenue with finger-snapping panache. She'll be at the Theatre of Living Arts on Aug. 6.

2. "Constructive Summer," The Hold Steady.

While his Brooklyn bar-band mates rock out, Springsteenesque storyteller Craig Finn dedicates a faithless promise - "We're gonna build something this summer" - to "St. Joe Strummer." From Stay Positive, on iTunes now and in stores July 15.

3. "Oxford Comma," Vampire Weekend.

There's been so much hype and backlash about Ezra Koenig's Ivy League foursome that it's been easy to forget what sets them apart in the first place: A knack for writing deceptively simple indie-rock songs. Their new single shows that even English grammar can be the stuff of breezy summer pop.

4. "Lollipop," Lil Wayne featuring Static Major.

No offense to Katy Perry or Coldplay, but the summer belongs to Lil Wayne. The at-once crude and inviting "Lollipop" is only the most mainstream of his current offerings. The dreadlocked New Orleanian is also garnering airplay with Tha Carter III's stuttering "A Milli" and his guest rap on Usher's "Love in This Club" remix. It's Weezy's world, we just live in it.

5. "Lolli Lolli (Pop That Body)," Three 6 Mafia featuring Project Pat, Young D and SuperPower.

Taken with Mika's "Lollipop" and the aforementioned Lil Wayne megahit, it seems that this Oscar-winning rap group is part of the season's pop-music oral fixation. T6M also uses a politically savvy ploy to get a potential paramour to disrobe: "Like Barack Obama said, it's time for a change."

6. "Dangerous," Kardinal Offishall, featuring Akon.

The hip-pop charts are an international playground. This destined-to-be-huge collaboration brings together Kardinal Offishall, a Jamaican-born Canadian producer, and Akon, the Senegalese American rapper who seems to have put behind him last year's dirty-dancing incident involving an underage girl.

7. "Chemtrails," Beck.

The first single from Modern Guilt, which comes out Tuesday, is produced by A-list knob twiddler (and Gnarls Barkley member) Danger Mouse. It finds Beck Hansen in an early '70s, Pink Floydish, ambient-rock mode. Trippy, adventurous and surprising, as usual.

8. "A Minha Menina," Os Mutantes.

With its great fuzz-tone guitar riff and psychedelic infectiousness, "A Minha Menina" sounds as fresh as it did 40 years ago, when it was a linchpin in the late '60s Brazilian Tropicalia movement. Now it's in a McDonald's TV commercial that debuted during the NBA Finals, and is being targeted for Olympic telecast saturation. By the end of the summer, it'll be the song you used to love.

9. "Little Bit," Lykke Li.

Gently percolating I-think-I'm-in-love song from the crafty 21-year-Swedish ingenue who is one of the breakout talents of 2008. Her EP Little Bit is out now; her debut album, Youth Novels, is due in August.

10. "Why Do You Let Me Stay Here," She & Him.

Fetching folk-pop from the grammatically challenged pairing of guitarist-producer-songwriter M. Ward and actress Zooey Deschanel. Him knows his way around tried-and-true melodies, while She puts Scarlett Johansson to shame in the singing-thespian sweepstakes. They'll be at the Trocadero on July 25.

11. "Always a Friend," Alejandro Escovedo.

Veteran Chicano chamber-rocker Escovedo rolls down the windows and puts the pedal to the floor, gas prices be damned, on this hard-charger, a highlight on what might be the strongest straight-ahead rock album of the season, Real Animal. He'll be at the XPoNential Music Festival in Camden on Friday.

12. "Girls in Their Summer Clothes," Bruce Springsteen.

Yeah, I know Magic came out last fall, and I've put this on mix CDs before. But sometimes you have to go with the obvious. The Boss' double-tracked voice has a satisfying Beach Boys echo. And the song captures an essential seasonal melancholy: Everybody seems to be having an excellent summer, except the singer of the song.

13. "I'm Amazed," My Morning Jacket.

My Morning Jacket's new album, Evil Urges, has been deservedly celebrated for its daring. But on this soaring blast of classic rock, the Louisville, Ky., band fronted by Jim James sticks to what it knows, cranks up the guitars, and gazes out at the world with a sense of wonder.

14. "Gobbledigook," Sigur Rós.

The chilly Icelandic experimentalists in Sigur Rós get positively giddy on the "la-la-la"-happy single from their new album, Med Sud I Eyrum Vid Spilum Endalaust, which translates as "With a Buzz in Our Ears We Play Endlessly." Not quite sure what has made them so excitable, though a look at the naughty video for "Gobbledigook" might offer a clue. (The band gets extra points for being ID'd by iTunes in the genre "Ewok techno.")

15. "Pork and Beans," Weezer.

With its crunchy chorus and smart-alecky verses, this is vintage Weezer. Rivers Cuomo sardonically quips, "Timbaland knows the way to reach the top of the charts / Maybe if I work with him I can perfect the art." Cuomo seems to be doing just fine on his own.

16. "Ur So Gay," Katy Perry.

Perry's "I Kissed a Girl," which tops the Billboard Hot 100, seems like the song of the summer. Though the cynical titillation of "Girl" yielded commercial success, "Ur So Gay" is catchy, nervy, and clever, while "I Kissed a Girl" is only the former two.

17. "Come On Over," Jessica Simpson.

In need of a music makeover, Simpson headed to Nashville, where, as Kid Rock and Jon Bon Jovi can tell you, pop-rock stars willing to swallow their pride are always welcome. The strumming guitars and sanitized let's-get-it-on lyric suits Simpson well, and this stands out among the country-pop competition.

18. "L.E.S. Artistes," Santogold.

From Bud Light Lime to Converse Chuck Taylors, Mount Airy's own Santi White has become the saleswoman of choice this season. (The band Santogold opens for at the Wachovia on July 25 - Coldplay - has also caught on.) The New Wave-electro synthesis of "L.E.S Artistes" shows there's plenty of songwriting substance to go with the style.

19. "Viva La Vida," Coldplay.

Speaking of Chris Martin and the boys, their red-and-blue soldier outfits may be patently uncool, but their way with a melody remains unassailable. Brian Eno's imaginative production helped, and resistance to this sparingly effective iTunes ad is futile.

20. "Shut Up and Let Me Go," The Ting Tings.

And speaking of Steve Jobs, the British duo of Katie White and Jules De Martino also have used an Apple ad - in their case, for an iPod - to get their music heard. Their tight, springy debut, We Started Nothing, packs plenty of pleasures, but the starting point is this winning disco-flavored conflation of Chic and Blondie. The play at Johnny Brenda's on July 23.

21. "I'm Not Going to Teach Your Boyfriend How to Dance With You," Black Kids.

Jacksonville, Fla.'s, Black Kids serve up handclaps and cheerleader-style backup vocals, plus a gender-confusing twist. "You were the girl I was dreaming of, ever since I was a little girl," Reggie Youngblood sings, taking this mix out on an ebullient high note. From Partie Traumatic, out July 22.