When it comes to talking to someone else via computer on the Internet, unless you have a microphone (headset integrated, desktop stand, built-in into the laptop) you really can't do much.
Well, having been a dj, sound engineer and radio station professional for quite a few years, I learned many years ago a trick, that even when I share it today, people have a hard time believing.
But there is nothing magic about this and it has all to do with how things work in physical reality.
Fact is that if you don't hve a microphone laying around when it comes to meet and discuss online at an important meeting, there may be indeed a very simple and handy way out.
Use a headset!
What!?!?! A headset as a mike?
You have understood me right and here is a little explanation for you.
The way most headset and earphones are built is not that much different from the way a mike is built. The mike has a thin membrane that captures sound vibrations and converts them into an electrical signal, while the earphone has basically an equivalent setup but with things going the opposite way. Electrical signals are converted into sound waves by a small membrane.
So if you plug most any type of traditional walkman-type headset, set of earphones of your CD player or anything similar into your computer microphone plug, you are effectively enabling a new use of your headset: sound input!
Notice, that it will be likely that only one of the two earphones will be a capable carrier of the your voice, for a number of technical reasons.
To find out if your headset works as a mike and to check which ones of the two earphones is the one to talk into perform a simple test while connected online with a friend through Skype or other voice-enabled application.
Talk into one of the earphones saying "ear one, ear one ...." and do the same in the other one saying something like "ear two, ear teo, ...". Ask now your friend when she could hear you better and in most cases you will find out that the right ear is the on that does the job right.
Far from being a professional microphone replacement, this solution is good enough for any emergency situation in which you suddenly do not have access to a needed microphone, while you have available a spare traditional headset / earphones set.
Last Thursday, during the Virtual Team 2005 online conference organized by iCohere, I facilitated a 90-minutes long online Q&A about grassroots online collaboration technologies. That day I opened the Q&A by sharing this very tip live with the present meeting attendees who happened to join in from many different parts of th world. Many were so excited by this possibility that wanted immediately to try my workaround. And so they did. Even if they had a working microphone they unplugged it and started using their headsets as a possible alternative backup mike to talk to me. As soon as they realized it wasn't an April's day joke, they fell in love with the newly learned trick.
Drawbacks: sound will be likely lower in volume and to obtain good results you will have to talk very close to the earphone bud.
This solution works with 85% of the commercial stereo headsets used for music listening as well as with earphones of different kinds.
Typical headsets have a stereo mini-plug just like the one adopted by all portable CD-players, MP3 players and old traditional walkmans. I have not tried ever with USB-based solutions and these may have some issues.
Go give it a try.