User script to make GMail chats wider. Then Google came out with Hangouts which makes this puppy obsolete.

fatchat.user.js

// ==UserScript==
// @name           GMail FatChat
// @description    Widens gmail chats considerably
// @namespace      http://chrisciollaro.com
// @match          https://mail.google.com/mail/*
// @version        1.0
// ==/UserScript==
 
 
//not pretty code, just wanted to throw something together that worked. google makes it tough by not giving many of their elements unique identifiers.
var listener = function(){
	if(document.getElementsByClassName('no').length > 2){
		document.body.removeEventListener('DOMSubtreeModified', listener);
		
		document.getElementsByClassName('dw')[0].children[0].children[0].children[0].children[0].addEventListener('DOMSubtreeModified', function(){
			var chats = document.getElementsByClassName('aXjCH');
			var chat = null;
			var greatGrandFather = null;
			for(var i = 0; i < chats.length; i++){
				chat = chats[i];
				greatGrandFather = chat.parentElement.parentElement.parentElement.parentElement.parentElement.parentElement;
				greatGrandFather.parentElement.parentElement.style.width = null;
				greatGrandFather.style.width = '400px';
			}
		});
	}
}
 
document.body.addEventListener('DOMSubtreeModified', listener);