1. Energetic - this is my all-time favourite! Great for prototyping blog style and 2 column brochure sites
2. Wilderness - excellent green theme for nature or environmental type website

I love the new Drupal 6 themes from Agileware Software located in Australia. These 2 are my favourite:

• Energetic  -   View Demo
• Wilderness  -   View Demo

I like the graphics - especially the rollover menu buttons. The menu highlights the button of the page that you are on. When you are editing your content, you get nice rounded coloured buttons for View, Edit, etc at the top of your page. The block theming looks great. Just swap out the graphics with ones with colours that you like, and you have a new theme in a very short time indeed.