Trials of the applications in Adobe CS4 are now available for download through the company website.
The trial version gives you 30 days to test the product after which you will need to register. You will also need to create a free account on Adobe's website in order to begin the download.
FYI: If anyone was worried about CS4 not being able to be installed on flash drives (the new MacBook Pro SSD drive for instance) don't worry. It's only for the Windows version of CS4 that rule applies. I have an SSD drive and am running CS4 Photoshop & In Design absolutely fine on it. Yay for Apple!