AOL fostered a new craze when their AIM (AOL Instant Messenger) made it easy for everyone to send a quick message to a friend or colleague. These impromptu sessions are very much like a phone call or a quick walk to someone else's cube, but without the physical aspects.
In literally seconds, you can start a conversation or ask a question of someone else. If they are available and have a moment, they can quickly respond. If not, your message will stay on their screen, like a voice mail or Post-It note, until they come back. At that point they can pick up the conversation easily and answer your question.
I know this sounds terribly simple, but the real power of these tiny, short, ad hoc conversations is how efficient they can be and how much productivity you can get without much interruption. Instead of stopping typing and looking away from the screen, picking up the phone and dialing someone's number, saying "hello" and asking a question, you just get right to asking the question.
That is very efficient on the sender's side, but even more efficient on the responder's side. They can be working on something else or taking a different phone call, get your quick message in a tiny window, and respond as they have time with little effort or distraction.
Here at our office, the staff and programmers shoot tiny questions and comments back and forth hundreds of times a day. For the Generation Y staff, they feel comfortable managing multiple conversations over IM, email and phone simultaneously. Those of us managing the staff have to remember that the younger generations can most definitely handle this level of multi-tasking and, to a great degree, expect it.
As far as which IM client is best, I've found the free packages like GAIM and Pidgin give you all the capabilities you need without all the advertising baggage that AIM, MSN and Yahoo bring along. Both GAIM and Pidgin are Open Source projects available from SourceForge, can connect to multiple services (AOL, Microsoft, Jabber, Yahoo, IRC, etc.) and support multiple user accounts from one client. Free, easy, popular, and flexible; a great combination.
You may be concerned about how much personal time might be wasted by opening IM to everyone in the office. You can certainly restrict who can reach which servers and thereby limit the conversations to just your office staff, but I've found that a little time spent gossiping with friends or coordinating with spouses for family logistics is a tiny price to pay when you unlock the hidden productivity you get from everyone using IM. If you still have to be secure or limit the reach of IM, you can use firewalls and chat servers to restrict their use without diluting the benefits too much.
Free software that delivers solid productivity gains and fosters rapid communication. What could be better?
Pidgin, the Open Source instant messenger client for AOL, MSN, Yahoo, Jabber, etc.
AIM, AOL's instant messenger client
Windows Live Messenger, MSN's instant messaging client