- Google Docs. (Web based.) Google Docs is part of the Google suite of office applications. A server-based application, it allows you to store files of up to 1GB in size for free. You can access your files from your mobile devices (including your iPad) as well as any computer with an internet access. You can save them to your device or computer in a variety of file formats, including ODF, HTML, PDF, RTF, Text, and Word. You can share access with other users, work collaboratively, and tag and archive your documents.
- Dropbox. (Free app.) Dropbox is a popular file backup, storage, and sharing service that has free and paid versions, up to storage of 100GB. There's a free iPad app that allows you to view photos, videos, documents, and presentations from your Dropbox on your iPad, share and send files via email, and export Dropbox files to open in other iPad apps.
- MobileMe. MobileMe is a service offered by Apple that will allow you to sync your desktop, laptop, iPhone, and iPad information (contacts, email, calendar, and files) together. Using the MobileMe iDisk, you can store your files online and access and download them anywhere, as long as you have internet access. You can also access and share files with other MobileMe users. With intuitive Mac interface, MobileMe is easy to use and quick to set up, but may not be the answer if you want to share with other, non-MobileMe users. $99 per year for 20GB of storage and 200GB of monthly data transfer.
If you're already using a file sharing/backup service, chances are, there's a way to use it on your iPad, and that's a great place to start. Why reinvent the wheel when you already have something that's working? Just do a quick search at the App Store and you'll see if there's a way to incorporate your iPad into your current systems. If not, check out one of the solutions above.