They traded Thad Young; Shane Larkin and Thomas Robinson opted out, and now word is that they are looking to dump Jarrett Jack if they can't trade him. If they waive him, they have a payroll of (* is dead money from waived players):

Brook Lopez $21,165,675 $22,642,350
Deron Williams * $5,474,787 $5,474,787 $5,474,787 $5,474,787
Bojan Bogdanovic $3,573,020 $4,466,275
Wayne Ellington $1,567,500
R. Hollis-Jefferson $1,395,600 $1,455,720 $2,470,357 $3,594,369
Willie Reed $1,215,696
Chris McCullough $1,191,480 $1,242,840 $2,243,326 $3,364,989
Markel Brown $1,180,431
Sean Kilpatrick $980,431 $1,051,245
Andrea Bargnani * $323,599

They also have Caris Levert and Marcus Paige from the Draft.

They're interested in Al Horford but is there any way that anyone signs with them? Could they somehow pull off a coup and sign a bunch of legitimate players and field an actual NBA team?

On the other hand, Brook's got a player option next year; if they can't sign anyone of importance, they pretty much have to trade him or they'll likely lose him for nothing.

Discuss the Celtics getting next year's #1 pick here.