I've found some great early contenders; if these are any sign it is going to be an awesome musical summer:
Katy Perry's California Gurls (and with Snoop Dogg!) - This song is an instant classic. The beat is incredible and the tone is just right for summertime sunshine and fun. Snoop's rap towards the end caps off what is already a fantastic song.
The National's Bloodbuzz Ohio - This one will certainly not make the standard S.o.t.S. lists, but I'd been looking forward to The National's new album, and this song is a somber, melancholic, borderline-completely-depressing treat!
Shakira's Waka Waka (This Time for Africa) - Yesterday I downloaded a bunch of music on iTunes and am so glad that, just before finishing, I came across the official album for the World Cup (which begins on Friday). I remember listening to the 1984 Olympics album endlessly and imagining myself as a sports superstar, and this album captures just the same dynamic. The songs are all about soccer/sports/world-togetherness, and they are incredibly uplifting. Waka Waka is super, as is...
Dario G's Game On - I was literally dancing down the street while listening to this and walking the dogs last night -- so uplifting and fun.
Shakira is from Colombia - I had not realized this. Her first language is Spanish and she also speaks English and Portuguese fluently. Here's an excerpt from Waka Waka:
When you fall get up, oh oh...
And if you fall get up, oh oh...
Cause this is Africa
Tsamina mina eh eh
Waka Waka eh eh