There are a number of programs for the iPhone that will allow you to listen to the radio. Most of them allow listening to formerly aired programs, much like a podcast.

Perhaps the most popular application like this is the ones National Public  Radio (NPR) operates in cooperation with local station affiliates. With the program, you can listen to the latest NPR newscasts, top national stories, and local news stories.

Not all local public radio stations have set up this mobile edition of NPR, however. Check with your local radio station.

Also, NPR - along with several radio partners - is developing a program that will allow you to listen to its programming in real time, just as it is being broadcast. But you don't have to wait for that program, MPR - Minnesota Public Radio - already has one for its signals.

Minnesota Public Radio allows listening of its three streams of audio in real time. With the MPR program - available as a free download from the iTunes Store - you can listen to the classical or popular music channels as well as the news channel, which is the main broadcast, heard in Minnesota on their network.

The live stream works using Wi-Fi or via the 3G or Edge network.

With good signal strength for these networks, the listening experience is robust. If you temporarily lose the network connection, then you'll have to restart the program and the stream.

One drawback of the program (really one of the iPhone OS) is that it does not allow multitasking. If your phone rings, or you want to browse the web, then you'll have to restart the MPR program to listen again to the stream.