Gasol would seem to be the most likely target, along with Love. They both play for teams with uncertain futures and aren't too old. I would be a lot more excited about Love if a defensive C like Gasol (or Embiid) was in the picture.
Actually, Gasol would be 30 years, 9 months old at the start of the 2015 season. That would be putting a lot of pressure on the team to win immediately. If you look at Pau's production, he's been slowing down the last few years at ages 30-33. Marc fortunately has less mileage but I wonder if the downslope of his career will be starting soon.
Some of the other names Deveney listed are unrealistic. Aldridge and Hibbert and Thompson are not going anywhere. Tyson Chandler will be 33 years old. Millsap is more of a borderline max talent. Faried and Jordan are not really versatile enough to be worth big deals, IMO.
Also, one thing obvious from these potential FA lists is the shortage of shooting talent at the wing positions. The Celtics need guys who can shoot to complement Rondo. One of those guys needs to also be able to create his own shot. This is the constantly brought-up "We are one dominating SG away from being a contender" problem.