If you use Live Communications Server and have a Windows Mobile device you need to have a look at Communicator Mobile.

A cell phone is not the ideal thing for a long IM conversation - even if you have a Bluetooth keyboard (as I do).
Sometimes, your phone is your only connection. Once in while I find it enormously helpful to check presence before making a call – usually when I’ve failed to reach one person and I’m thinking about who to call next (you can start a call or message from Communicator Mobile as well as IM). It’s one of those tools that you don’t use every day but it’s very useful when you do use it, a bit like the >Sat Nav software I also have on my phone. I’ve even had someone IM me the address where we were due to meet, and fed it into the Sat Nav.

It does make me wonder who wants to carry an iPOD, a Blackberry and a phone, AND have a sat nav device in the car.