If salary situations remain as they are around the league in 2012, Boston is probably the second most appealing destination for Dwight Howard if he makes it to free agency. Dedicated ownership group, well-respected coach and management, all-star PG in his prime, fringe all-star wing in his final year, the possibility of Ray and KG re-upping for cheap... Very strong pitch, the best immediate shot at contention.
New Jersey will have a stronger case in my opinion. They have the more highly-regarded PG in Williams, and though their supporting cast of Morrow, Outlaw, Petro and Farmar is underwhelming, it's not locked up long-term.
New Orleans could jump to the forefront if they can find takers for Jack (easy) and Okafor (harder, but not impossible). With CP3, Ariza and a southern, warm-weather locale (provided they stay in NO), I think they'd be Howard's preferred choice.
Houston could also be a dark horse. No all-stars, but Lowry, Martin and Scola are very nice players. Warm-weather, respected management, winning tradition.