Here are the chat hyperlinks that I know of. Just enter your username where it says USERNAME and then copy and paste the whole code line into your website / forum / chat signature, whatever.
When someone clicks on it, they can instantly send you a message. Obviously, apart from the href, it is a standard HTML link, so you could change “send me a message” to something else if you’d prefer.

Windows Live Messenger: (the username is the Hotmail address)
<a href=”msnim:chat?contact=USERNAME”>Send me a message</a>
Yahoo Messenger:
<a href=”ymsgr:sendim?USERNAME”>Send me a message</a>
AIM:
<a href=”aim:goim?screenname=USERNAME”>Send me a message</a>
Google Talk: (the username is the Gmail address)
<a href=”gtalk:chat?jid=USERNAME”>Send me a message</a>
Skype:
<a href=”skype:USERNAME?chat”>Send me a message</a>

Whether the user actually has any of these tools installed is another thing. In firefox, for example, they may get the message The protocol is not associated with any program.

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