How to implement intranet

My company has requested that I create an intranet solution. They want employees to access from the Web. It needs to be secure and capable of transferring files as well. I'm not sure that an intranet is exactly what they're looking for. I've seen the term 'portal' in the research I've started, but I'm primarily an Windows developer and don't have any experience with the necessary infrastructure. Can anyone make any suggestions? Books, directions or anything is appreciated.