Facebook has gone out of its way to inform me that Joseph Arthur has formed a supergroup with Ben Harper and George Harrison's son called "Fistful of Mercy." I listened to the first track, and it sounds like a slightly peppier Joseph Arthur (not that there's anything wrong with that), but there's nothing there that made me say "wow, now that these three have come together, there's gonna be amazing things happening!" But it did inspire me to consider my favorite supergroups of all time:

10. The Dirty Mac 
Created for a special Rolling Stone concert. They played together just once, but can you imagine if they'd made a record?
Key Players: Eric Clapton, John Lennon, Keith Richards, Mitch Mitchell (The Jimi Hendrix Experience)
Best Song: N/A

9. Me First and The Gimme Gimmes
Concept albums featuring punk covers of songs from a particular time period/style (musicals, country, the 60's)
Key Players: Fat Mike Burkett (NOFX), Spike Slawson (Swingin' Utters)
 "Leaving On A Jet Plane"

8. Velvet Revolver
A failed attempt to prove that Weiland could stay in a band for more than 5 minutes, before their label released them so they could get rid of him. Those 5 minutes were fun, though.
Key Players: Scott Weiland (Stone Temple Pilots), Slash (Guns N' Roses)
Best Song: "Slither"

7. The Dead Weather
Jack White once lost his voice and asked Mosshart to fill in for him during a White Stripes show. Apparently, magic happened.
Key Players: Alison Mosshart (The Kills), Jack White (The White Stripes)
Best Song: "Treat Me Like Your Mother"

6. Broken Bells
Indie pop sensation meets with indie rock superproducer (Beck, Gnarls Barkley, The Black Keys) for slightly monotonous, occasionally brilliant synth pop.
Key Players: James Mercer (The Shins) and Danger Mouse (Gnarls Barkley)
Best Song: "The High Road"

5. Traveling Wilburys
The first real supergroup, to which all supergroups are compared.
Key Players: Boby Dylan, Tom Petty, Roy Orbison, George Harrison, and Jeff Lynne
Best Song: "End of The Line"

4. Audioslave
A somewhat successful attempt to prove Cornell could stay in a band longer than 5 minutes, the band broke up in 2007 over "irresolvable personality conflicts as well as musical differences." Shocking.
Key Players: Chris Cornell (Soundgarden), Tom Morello (Rage Against The Machine)
Best Song:  "Cochise"

3. Broken Social Scene
A rotating crew of members of the Toronto indie scene.
Key Players: Almost 20, including Torquil Campbell and Amy Millan (Stars), Feist, and James Shaw (Metric)
Best Song: "Stars and Sons"

2. Bad Company
So memorable as their own act, I hadn't even realized this was a supergroup.
Key Players: Paul Rodges (Free), Mick Ralphs (Mott The Hoople), Boz Burrell (King Crimson)
Best Song: "Bad Company"

1. The Postal Service
A name coined by Gibbard and Tamborello's need to ship the tracks back and forth while they worked on the songs. Poppy indie electronica.
Key Players: Ben Gibbard (Death Cab for Cutie), Jimmy Tamborello (Dntel), Jenny Lewis (Rilo Kiley)
Best Song: "We Will Become Sillhouettes"

And, on the flip side, my least favorite

Alter Bridge
The guys from Creed tried to prove that they'd be a better band without Scott Stapp. Incredibly, this turned out to not be true.
Key Players: All the guys from Creed minus Stapp, plus Myles Kennedy (The Mayfield Four)
Best Song: N/A