Webex
The best of the best. Web-based online meeting tool. Works fine with IE and Firefox. You can show,share,edit document. You can also give full control to your desktop. Chat, Video, conferecnce calls.etc.,
Google Word (Writely) - Free
A lovely free web based word editor. Has more or less all features that your Desktop PC word processor has.
Google Spreasheet - Free
You can not only create a spreadsheet online, but you can also share it with others.
Google Calender - Free
Certainly a great online organizer. It can even send you reminders emails for forth coming events. You can also share your calender with others.
Skype - Free
If you are reading this, then for sure you are part of it. I normally use webex with skype to avoid international telephone charges.