http://espn.go.com/nba/tradeMachine/?tradeId=b64ng7oBoston:Josh Smith
Big Al
Bledsoe
LAC:KG
Utah:Pierce
Atlanta:Jordan
Boston does it because they get younger and add 3 young pieces to a young nucleus, which also includes Rondo, Bradley, Green, Sullinger, Lee, etc.
The Clippers are in "win now" mode and the Jordan & Bledsoe for KG has been much discussed.
Utah is loaded at PF/C, but have a major weakness at SF and overall perimeter scoring. Marvin Williams is their current starter and is averaging 8 ppg and 3 rpg on 42% from the field and 33% from 3's. They're also not likely to re-sign Big Al and Pierce still has one year on his contract should they choose not to waive him. The deal makes them better today and gives them options next year.
Atlanta is 2 days away from letting Smith walk for nothing. They have also wanted to move Horford to his natural PF spot for some time. Jordan gives them young return value and allows them to move Horford to the 4.
Perhaps Atlanta gets a few picks from a couple of the teams, but the above is basically the key pieces of the deal.