A couple of coders in Austria have developed what they have correctly named The Most Simple Ajax Chat Ever.
Their chat application is indeed very simple — there are no buddys, handles, logs, or fancy tricks, just a chat room full of anonymous users kibbitzing. They have built in spam controls, however.
Three files make the chat function: an HTML file to handle the text input and the display, a TXT file containing your chat message that's generated on the fly, and a PHP file to pass your inputted text. The app also uses only 2 HTTP requests. Ajax at its simplest?
Check out their page at Linuxuser.at to test out the chat and to view their slim source code.
[link via del.icio.us]