Tokbox: Add up to 20 people to your conference. The best part is they dont have to have a tokbox account. Simply send them the url of your conference and they can join up. Tokbox also has a twitter button that will send the link twitter friends so they can join up too.
Boostcam: Instant / disposable video conferencing. No username and no password required. Very simple to use. Would be great for people who are a little scared to connect for the first time.
FileinaFlash: Send files over the internet by just sending out the url. No username or password required. Most email services will not let you send a file over 20 megabites so if your in a pinch use this to send large files.