Is it possible to use extensions on the developer build of Google Chrome for Mac? Ive seen tutorials for windows and linux.
At this exact moment, you need a trunk build. You can get one here:
We hope to turn extension support back on in the next dev channel release of Google Chrome for mac.
Have a look at this: Enable extensions in Chromium (or Chrome) – Mac OS X Hints
I would also look here for more information: Chromium-extensions
For reference the current version of Chrome supports extensions and has since February 2010.