iPhone cannot connect to some Wi-Fi networks

It appears that iPhones cannot (we haven't yet found a method, anyway) connect to certain types of Wi-Fi networks. Specifically:

• 802.1x/PEAP: used by some networks to provide port-based security/authentication by passing Protected Extensible Authentication Protocol (PEAP) over a LAN. The desktop version of Mac OS X has supported 802.1x since Panther (Mac OS X 10.3). This standard is used by many corporate and educational institutions.
• Some Web-login Wi-Fi hotspots: Wi-Fi hotspots that require Web-based login. Particularly T-Mobile hotspots, and some systems used for city-wide Wi-Fi access. Some Web-based logging systems appear to work, others do not.

If you've had success connecting to either of the aforementioned network types, please let us know.