I updated Transpose to do the job of auto copy text to clipboard in Chromium, Firefox and Opera based browsers.
The way it works, select text with the left mouse button. Press the Alt key before releasing the left mouse button. On release of the key and mouse button you should see the text deselected. It should now be in the clipboard.
It's just a macro sending Control-c and later a left click to deselect the text. But it has the virtue of being independent of Addon or Plugin code.
The updated source is included. I created a new group BrowserGroup in the ahk source. If you wish to add another browser just use the ahk spy tool to get the ahk_class name of that browser and recompile.
edit: I just tried it with IE 8 and it doesn't seem to like it. But I like the action and use Chromium or Firefox for 99.99999% of my browsing anyway.
If you're into IE perhaps you can change the hotkey to something compatible if there's no reliable auto copy type addon for it. I don't use it enough to know.