A new, very Web 2.0, startup called Zoho is trying to do AJAX office apps. Now, reportedly, they're pretty awful. You have to sign up to use them, and it doesn't seem to work in Safari (it fails rather ungracefully, with a big brown screen), so I haven't bothered actually checking.
However, I can confirm that their login screens look frighteningly like Google's, though they do have odder URLs. Perhaps they aim to make any acquisition particularly easy? They'd basically just have to change the logos. For a proper company, it is amazingly rip-off-tastic.