Telegram is a cloud-based and open protocol instant messanger. At the moment it's the number one contender for IRC, amongst teekkaris.
Telegram is extremely easy to use, just download the app on your mobile and follow the instructions. Telegram homepage has lots of additional information and asking around is never a bad idea.
Skilta has an english-only channel for all our international students: Skilta International. Skilta also has newsflash channel Skillan tiedotus, however it does not replace the e-mail newsletter.
On mobile, Telegram app can be downloaded for Android, iOS and WP devices.
Telegram also has an excellent deskop app for Windows, OSX and Linux systems.
Telegram can also be used via their web application.