Apple opened the beta of iWork for iCloud to all iCloud account on Friday. Apple had previously limited the beta to first developers, and then to select iCloud members through invitations, but now any iCloud account appears to have access to the beta.
Apple didn't announce the move, but Italian site Spider-Mac first noted that the apps were accessible by non-developer and uninvited accounts. That was picked up by Engadget and other sites, and thus is Apple's work often accomplished.
If you want to play around with Pages, Numbers, and Keynote in a browser, login to your iCloud account and have at it. The icons for the apps won't appear until you are logged in.
Here's a taste of what's there now:
Pages, Formal Letter, in iCloud