The Essential Theme, maintained by Gareth Barnard, is by far the most popular Moodle theme. Ever. It is downloaded thousands of time per month from Moodle.org and (according to Moodle stats) is currently supporting almost 10,000 sites.
If you’re unfamiliar, check out this overview of Essential:
Gareth would like to update Essential for 3.0, but as you know, this work is neither easy or cheap. The folks over at Moodle Garage have put together a croudfunding campaign to help Gareth offset the costs of bringing Essential up to snuff.
They are seeking to raise 500 GBP (about $750 USD) and, as of this posting, have already received 1/3 of the funds.