There are millions of ways to speculate as to where he'll end up. Lets look at it simply though:
1) Bulls - He could possibly end up in Chicago merely for the reason that he's still close to Akron, his hometown. Another possible reason is that Jordan has been his idol and im sure he would love to play for the same team. However, as for a supporting cast, the bulls have some great players but the problem is that they are all young. Some would argue they are too young. Derrick Rose is a great leader and he is the reason the Bulls made the playoffs this year. If Lebron goes to Chicago the entire dynamic of the team is going to change and not necessarily for the better. Clashing egos is never a good thing.
2) Nets - The Nets lack leadership, which is something Lebron can easily provide. The fact that they have a new billionaire owner is completely irrelevant because the team can only sign players to contracts within the salary cap. I believe that the nets only have enough space to sign one maximum contract player, which in this case would be Lebron. So that would mean that the Nets would not be able to provide him with an All Star caliber free agent. My guess would be that if he were willing to actually join the team, the only person who could convince him to do so would be Jay-Z, part owner of the team.
3) Knicks - The Knicks have been waiting for this day probably longer than any other team in the league. There are MANY people out there claiming that the Knicks don't have enough money or talent to provide Lebron with a Championship caliber team, but the Knicks are the only team in the running that has the capability to sign 2 maximum contract players and still remain under the salary cap. As for the talent, the Knicks are very similar to Nets in that they lack leadership. This past year they dumped a bunch of players (and their contracts) and picked up Tracy McGrady (who seems to be just a presence in the locker room). Being that it is New York, Lebron has access to the greatest level of exposure. With the prospect of being able to sign a second free agent (Amare, Bosh, Joe Johnson, or D-Wade, and rumors of Tony Parker wanting to play in NY), the Knicks have a lot to offer.
4) Cavs - Will he resign with the Cavs? Maybe. Being that he's basically playing in his hometown is something that is going to be important to him. But will this team get him a championship? No. They dont have enough money to try and woo one of the aforementioned free agents. Also, it seemed like he gave up in that last game against Boston...not sure what that means though.
5) Clippers - Never going to happen....not much else to say about that.
Lebron loves drama and he's going to play this out until the very end. He loves the media attention. This summer, he could quite possibly take over the Dos Equis commercials as the Most Interesting Man in the World