Dropbox is the easiest way to sync your files online and across computers, and share them with people.

With MobileMe iDisk, you can view and share the files on your iDisk right from your iPhone or iPod touch. MobileMe subscription is required.

Allows you store multiple file formats and is great for reading large PDF documents.

FileMagnet makes it easy to copy files from your computer onto your iPhone and iPod touch. You can view all the popular file formats, including PDF, Microsoft Office, RTF, and iWork '09, even when you're not connected to the internet. Transferring files is effortless — FileMagnet wirelessly connects to your computer using a free program

The easiest way to view your documents on the go.

Box.net is an online file sharing and collaboration service that lets you easily access your files from anywhere and securely share content with anyone. The Box.net app lets you view and share files in your Box account on-the-go.