Quick update: now that Ubuntu GNOME is an official Ubuntu flavour, it can make use of the Ubuntu infrastructure, and the first daily builds are now available for download:
Currently we have 32-bit and 64-bit images available for download and testing. We do not plan to release PowerPC or "amd64+mac" images unless a group of volunteers commits to test these images for each of the Ubuntu release milestones we participate in. The next release milestone for us is Ubuntu 13.04 Final Beta on 28 March.
- Matthew Butler @ Ubuntu GNOME mailing list
Oh, and I've forgot to mention this in the previous Ubuntu GNOME article: if you can help in any way (not just packaging and coding), including reporting bugs, join the (new) Ubuntu GNOME mailing list or the #ubuntu-gnome channel on the freenode IRC network.
Download Ubuntu GNOME daily images