If you're like me, who do presentations to customers etc and would like to do at the comfort of your office space, then try http://www.vyew.com/.
I've used it several times thought I'd share it this time around.
It is a free (and has a commercial) pure web based (flash) conferencing software that enables you quickly setup online presentation meetings and invite people while using just their browsers. Import word documents, PDF, PowerPoint and images and start presenting! It can also share desktops live, import screen captures and plug-ins.
It connects on HTTP(s) and if you require file transfer, then you need port TCP9102 and TCP9100, otherwise, simply use the default HTTP (80,443) to connect. It has a simple chat bar and can do free voice conference calls (within US) but you pay your normal long-distance calls if you are outside the US (sigh, otherwise, this would rock for my prezzo in the morning!). So now, i've just have to conf-call my clients ol' skool.
Apart having a funky color skin, this piece of tool is good enough with its free package that can offer up to 20 users per session. If you like it and want to have more connections, get the commercial version.
Well done Vyew!