Wikipedia's article on the "History of Myanmar" is usually at the top of any Google search for material on the history of Burma.
It's a pity that there really isn't much there yet. For example, the entry on Dhammazedi is only a stub waiting to be filled in with the essential details of his life. The Bayinnaung entry only has a rough sketch for such an important king.
I am continually finding exceptionally good Wikipedia entries for the learning English with the newspaper articles I write each day for the Bangkok Post. Like yesterday I found a great article on collaboration and another one on incentives.
I started working on the page a little bit today by adding what I find to be some of the most useful links for the history of Burma.