I wrote an article some time ago about how to Hyperlink to Messenger Applications but at the time I couldn't find how to hyperlink to Google Talk. Thanks to Jaspreet, that mystery has been solved. Below is an updated list of how to link to messenger (instant messenger) applications.

AOL Instant Messenger: aim:goaim?screenname=#screenname#

Google Talk: gtalk:chat?jid=#google email# or gtalk:call?jid=#google email#

MSN/Windows Live IM: msnim:chat?contact=#screenname#

Skype: skype:#screenname#?call or skype:#screenname#?chat

Yahoo! Instant Messanger: ymsgr:sendim?#screenname#