This really depends on just exactly what you mean by sharing documents, and what you really mean by safe and secure. Safe and secure really is only reletive to how interesting your information is to someone else, and just how determined that someone else is to get their hands on your data. With that in mind, there are four distinct ways that immidiately come to my mind that fit in to two categories. Collaborative sharing and document/file sharing.

Collaboritive sharing is a scenario in which a document is created and stored in a central location allowing multiple users to access and modify that document. There are two popular, and free, services that I use from time to time. The first is Google docs (http://docs.google.com). Google docs has several features such as document creating, uploading and downloading, and is compatable with multiple file formats. It also has online storage and an online word processor so that the user is not required to actually have an installed word processor such as Microsoft Office or Open Office in order to work with the documents. Within the Google docs online application there is a clearly marked button labeled "Share" that allows you to choose other Google users and grant them read or collaborator rights to specific documents. The only drawback that I've been able to find is that other users must have a Google account in order to interact with your online documents. Benefits are online storage, support for multiple document formats, and online editing so that documents can be edited from any computer regardless of the operating system, and whether or not the computer has any word processor installed.

The second is OfficeLive (http://smallbusiness.officelive.com/), a Microsoft service. OfficeLive differs from Google docs in that you must have Microsoft Office on your local machine in order to interact with the shared documents. Also, Office live does not yet have an online word processor so you must create your documents on your own computer and upload them. You can share your documents and they can be read online, but in order to edit documents they must be downloaded to your machine, edited in Microsoft Word, and saved online again. This is not a drawback if all users have Microsoft Office Installed on their machines, but it is more limiting than Google docs. Benefits include online storage, nearly full integration with Microsoft Office (spreadsheets; Word documents; Outlook contacts, tasks, and calendar).

The second category is simple document/file sharing. Possibly the most secure way to share files between people who know each other is the BitTorrent protocol using a BitTorrent client. In spite of what many would have you believe BitTorrent is not inherently illegal or even unethical. It is simply a way of transferring data from one computer to another, and many legitimate sources use BitTorrent as their primary way of distributing data. As long as you own the data that you are sharing, there is no legal issue using the BitTorrent method. I discuss the following with that in mind. Many BitTorrent clients, such as uTorrent (http://www.utorrent.com/) provide a tool to create your own torrent files. The BitTorrent client will scan your specified file and create a small file with a .torrent extension that provides data about the file, or files, you want to share. You will mark the specified torrent as shared in your BitTorrent client, and send the .torrent file to the person or people with whom you would like to share your data. They will import the .torrent file in to their client, and download the specified data to their computer. The benefits are that only the people who have a copy of your generated .torrent file will be able to download your data, and the more people who share your data, the faster your data can be shared.

Finally, you could simply use a compression tool such as WinZip (http://www.winzip.com/index.htm) or WinRar(http://www.rarsoft.com/) to compress the file(s) and password protect them. Then, you use your method of choice to get the compressed file to the other person. Since the compressed file is password protected and encrypted, the data will be secure even if someone else manages to intercept your data. The drawback to this method is limited by the method that you choose to share your data with the other person or people.