IT security company Sophos has warned GMAIL users that a phishing attack is underway via the Google Chat system. Users have been receiving chat messages with a "check this video" message and a tinyurl link. Once clicked, the link redirects them to ViddyHo, a site where they are asked for their Google credentials. Hackers can then re-use this information to snoop in people's accounts and possibly use the information to steal one's identity.
Be careful in general, and it seems like a good idea not to use one site's credential (Google's) on another site, that just sounds like "give me your login and password". More stories about this on the web.