A page without TLS (aka SSL) is not secure against eavesdroppers or Man-in-the-Middle attacks. I wouldn't give them any information I want to keep secret like credit card #s or passwords that I don't want to fall into the hands of an attacker. I will however say use dumb passwords for accounts that I don't worry about falling into the hands of an attacker (like a free account to read washington post articles).
Granted that doesn't mean any user on the network can always trivially to eavesdrop/launch a MitM attack. E.g., most LANs are set up in a star network topology, meaning that unless you have access to the central switch (typically only administrators or people working at an ISP), its not easy to eavesdrop in.
Granted say unencrypted wifi is different and makes it easy to eavesdrop. Even wifi with a broken security scheme like WEP or where you know the pre-shared key and observe the WPA handshake that generates the pairwise transient key.