Ray Allen + Brandon Bass + Jermaine O'Neal + E'Twuan Moore
for
Lamar Odom + Shawn Marion + Roddy Beaubois + Ian Mahinmi
Celtics get two cheap young prospects and a couple decent veteran roleplayers on short / non-guaranteed contracts.
Mavs get two valuable players on expiring deals (doesn't eat into their capspace), an old but not totally useless backup center, and a young SG for filler.
Could throw in the Clips pick (will be late in the 1st round) if necessary to entice the Mavs.