Install Cactus with the following one liner
sudo easy_install cactus
If you saw no errors, you can now generate a new project
cactus create ~/www.mysite.com
To start editing and previewing your site type the following. Then point your browser to localhost:8000 and start editing. Cactus will automatically rebuild your project and refresh your browser on changes.
cd ~/www.mysite.com
cactus serve
Once you are ready to deploy your site to S3 you can run the following. You will need your [Amazon access keys][5]. If you don't have one yet, [read how to get one here][6].
cactus deploy
Voila. Your website generated by Cactus and hosted on S3!