There are a lot of different ways to communicate inside companies. In smaller businesses it’s more likely to just talk to each other or send emails. However, if the company grows there is a point where companies need to offer additional ways to exchange information. One of these additional technologies would be instant messaging. There are multiple providers of such applications, most of them are hosted outside of your company. With Intrexx it’s possible to integrate the free real time collaboration server Openfire for XMPP(Jabber) into your company portal using a jQuery XMPP plugin. Openfire can be hosted in your own environment, used for free and is therefor a good alternative for instant messaging.
As most of the people I also don’t like to reinvent the wheel. This is why, when I have to code something, I try to use existing, usually even free, code libraries to work with. Since most of them are also open source, I can be pretty sure they are of high quality and used and tested very often.