BitTorrent Sync would be worth trying for file sharing - Create a folder with your friend's name and give that person your shared secret generated for that folder. That person can then create a folder with your name. Repeat with any other contacts you would like to exchange files with. When you want to share a file with someone, just drop the file in that person's folder and it'll sync automatically. The same vice versa where someone would like to share a file with you - they drop it in the folder they created for you and it'll sync to the folder on your PC with their name.
The big advantage with BitTorrent sync is being able to share what you like, unlike MSN where I've had files fail due to someone trying to share a software utility, etc. executable or certain zip files.