Tactics board
I found a useful web-based tool to discuss tactics. Here you can draw or write anything and other people can see it immediately. Rodrigo can draw a tactics board here, I think it's faster than telling the positions in chat and gives more information. Now I explain how it works.
Here is the website: http://www.twiddla.com/
You don't have to register, just click on the button "Go start a new meeting".
To invite people to the meeting give them the address of the page. (for example: http://www.twiddla.com/543255 ) So they can join and see what you draw. They can draw or erase as well.
With the tools in the top of the page you can select which tool you want to use.
You can:
| open an image | draw | erase | draw shapes | write text |
 |  |  |  |  |
Here is an example I made:
First I use this field template, open the image in twiddla:
http://dl.dropbox.com/u/26394463/board.jpg
It looks like this:
So you don't have to draw the pattern of the field.
Here is the finished tactics board example:
