http://www.icq.com/whitepages/about_me.php?uin=1
aim:goim?screenname=1.com&message=Hi.+Are+you+there?
http://edit.yahoo.com/config/send_webmesg?.target=1
The only usable field today is the website link field and maybe a Bitcoin address.
btw. How old is this, they are still HTTP links even though they switched to certified urls a long time ago
I thought more about link text then the links itself. Unfortunately links for ICQ, YIM, MSN are automatically generated and they can not be changed or disabled. But link text may be used just for text purpose. Not the most elegant solution but it is what it is.
Besides website field there are Skype / location / other contact info / bitcoin address fields that are in my opinion very useful too. They can hold a lot of content and also they can support emojis.