The new MobileMe iDisk app is free, but of course it entails having a MobileMe account, which runs $99 per year. I like MobileMe, which automatically keeps my contacts in sync with my contacts on my computer. Add a new contact to my computer, and it's automatically there on my iPhone. I also recently began using MobileMe's iDisk, which lets you store files online, and combined with Apple's free Backup application, lets you automatically back up selected files and folders on your computer. Remote backup is crucial. Now the new MobileMe iDisk app lets you view the files that you have stored on your iDisk on your iPhone (though you can't edit them). It also lets you share those iDisk files with friends via your iPhone. Say you're out and about and you want to show someone a spreadsheet you have on your computer that is also backed up on iDisk. You select the file using MobileMe iDisk on your iPhone, then conveniently select an e-mail address from your contacts, then click send. The person receives an e-mail with a link to the file. You can more about it on TidBITS.