You could perhaps try Quiknets.com (Windows/ IE). When you register there you get a Private Box, InBox, email, Workspaces, ability to make a folder to share with named others chat, etc. Under Extra Content, you can download some FCRLite encryption. That allows you to make "self extracting" encrypted files/folders. When the user enters a password (any password you choose and convey to him), even if he doesn't have the encryption program. Files are always stored as you send them and are encrypted under a password only you know. You can send to any email address, as well as transferring an encrypted object to any Quiknets member privately.
In addition, you can right-click any file/folder in Quiknets and "copy the link", and then use that url to make a "login link" to it in Netsso.com. From any PC, Netsso will then bring you direct to the file, including logging in your Quiknets credentials, when you simply double-click the link.