I use Dropbox, you can get an app for your iPad and your Mac/PC, you then just drop a document into it and as if by magic, it appears everywhere else that you have a Dropbox app, you can also use it to share documents with others.
If you have other Apple products or are interested in other Apple kit then why not join our sister forum too at http://www.appleforums.net/
Finally, if you still haven't had enough, how about a video explaining about our other forums (note:you may want to play this at half speed but hey, why shouldn't Phil be excited about our forums!)
GoodReader is another good app that can transfer documents to and from the iPad over WiFi. It's the iPad's 'Swiss Army Knife' and has a whole load of other uses to, so it might be worth checking it out in the App Store.