The greatest browser in the world has a revolutionary update in the form of an alpha build, codenamed Peregrine.
Those using this new build will also notice that the in-line spell checker is set to US-English as the default dictionary. To change it, this is what you do:
Opera uses OpenOffice dictionary files. Just download them and unpack the contents to your Opera profile/dictionaries directory, which will generally be located at and restart Opera to make it selectable.
Note: The English-GB dictionary does not seem to work with Opera. However, the English-OED (oxford english dictionary) link on the page does the trick.
This first alpha features the new Presto 2.2 engine, which is faster and more standards compliant than previous versions. Among other things, it achieves 100/100 in the Acid3 test, supports Web fonts, styles XML documents, supports CSS RGBA and HSLA colour values, the W3C selectors API, and more.
You can download the latest Opera beta build here.