A low-overhead web-based chat system, Meetings.io lets you video chat with up to five people at once while adding in screen- and file sharing as a bonus. Regular users (such as service providers who want to encourage customers to initiate paid web chats) can create a profile page on the service with a static URL, but otherwise no signup is needed to use the system. Registered users can calendar meetings, importing contacts from email, Facebook, or LinkedIn to manage the invitee list. Works fantastically well and costs nothing.
Pricing: free (up to 5 participants)