Nice overview of the laws regarding the use of cameras on public property. The short version is that, "If you can see it, you can shoot it", although there are some important subtleties and exceptions that are covered in the article:

Let's get the easy stuff out of the way. Aside from sensitive government buildings (e.g., military bases), if you're on public property you can photograph anything you like, including private property. There are some limits -- using a zoom lens to shoot someone who has a reasonable expectation of privacy isn't covered -- but no one can come charging out of a business and tell you not to take photos of the building, period.

Further, they cannot demand your camera or your digital media or film. Well, they can demand it, but you are under no obligation to give it to them. In fact, only an officer of the law or court can take it from you, and then only with a court order. And if they try or threaten you? They can be charged with theft or coercion, and you may even have civil recourse. Cool...

It gets better.

You can take photos any place that's open to the public, whether or not it's private property. A mall, for example, is open to the public. So are most office buildings (at least the lobbies). You don't need permission; if you have permission to enter, you have permission to shoot.

In fact, there are very few limits to what you're allowed to photograph. Separately, there are few limits to what you're allowed to publish. And the fact that they're separate issues -- shooting and publishing -- is important. We'll get to that in a moment...

You can take any photo that does not intrude upon or invade the privacy of a person, if that person has a reasonable expectation of privacy. Someone walking in a mall or on the street? Fair game. Someone standing in a corner, looking at his new Prozac prescription? No. Using a long lens to shoot someone in an apartment? No.

Note that the limits have nothing to do with where you are when you take the shots; it's all about the subject's expectation of privacy. You can be on private property (a mall or office-building lobby), or even be trespassing and still legally take pictures. Whether you can be someplace and whether you can take pictures are two completely separate issues.

The whole thing is worth reading, especially if you have a new digital camera or camera-phone. (Via Clicked.)