Boingo Wireless claims to be the worlds largest network of Wi-Fi hotspots. They have just released Boingo Mobile for BlackBerry which lets you authenticate to their hotspots from your BlackBerry. I cannot say if it was possible to do this before using the built in client but this is Boingo’s officially supported solution.
You can download the client OTA at this link or also find it in their Download Center. The client is still in beta but gives you one click access to over 100,000 hotspots Boingo runs. Right now the app only runs on the BlackBerry Curve 8900, BlackBerry Curve 8320, and BlackBerry Bold smartphones but support for more devices is coming soon.
If you give it a shot let us know what you think!