Xrender extension docs anywhere?

I'm interested in knowing what extensions have tried to address
improving the performance and visuals for drag operations, such as
those commonly used by graphical file managers. 

(i.e. currently dragging a filemanager icon around is a heavyweight
window which causes lots of expose events, can lag behind the cursor
if the machine gets instantaneously busy, and isn't drawn perfectly at
all times because of delays in the shape extension's filling in of the
regions around the icon.)

Some stuff I found implied that XRender might do something about this,
or at least might help. However, all the links I can find to XRender
are either dead, or lead to pages where all the links are dead. 

Can someone (Keith?) point me to an up-to-date site?

-- 
David Jeske (N9LCA) + http://www.chat.net/~jeske/ + [email protected]