You can use Otixo to save Pages/Keynote files to Dropbox or Google Docs directly from the app. This blog post on How to Use Pages for iPad with Most Cloud Services gives directions on how to get set up.
Send to Dropbox gives you a unique e-mail address that you can use to forward attachments from your e-mail to a Dropbox folder. Of course, this will also work when accessing your e-mail on a laptop.
This blog post, Saving Documents from iPad to Dropbox, suggests one way to save Pages/Keynote files to Dropbox on the iPad; it’s not the most elegant solution, but it does work.