Starting today, you can use Skype with up to 50 video chat participants, as part of a new update of the stable version of the application. Today's update consolidates Skype as the clear winner of group video chat, at least in terms of the total number of people you can have in a single call, since FaceTime only supports up to 32 participants. Previously, Skype only supported up to 25 calls at a time, although the new 50-person feature has been in testing for beta users since early March.
To have a better handling of so many participants, Microsoft has improved the group notifications a bit. Before the update, each person would receive a ring when a call was initiated. Now, however, the Skype application will usually send you a system notification for large calls, and you can specify which participants can really sound to you. However, Skype will still allow a call organizer to ring everyone if there are less than 25 people in the group.
Large group calls are available for Skype users that are updated to the latest version of the application as of today.