There are plenty of websites explaining, some even generating, Social Bookmark Links.
In this blog I would explain how to manually handcraft these bookmarks. Once you have understood the concept of bookmarking code then it would become a piece of cake for you to write your own script to generate it or play with it in manner you want.

Above is an example of Bookmark button for del.icio.us
The link for above icon is simple. The main thing to look for is the href part of link
href="http://del.icio.us/post?url=http://www.SwamiWebDesign.com&title=SwamiWebDesign"
Following are the main components
1) The Bookmarking website URL to post bookmark
http://del.icio.us/post
1) The URL of the website which you want to book mark
http://www.SwamiWebDesign.com
2) Title of the website to be bookmarked
SwamiWebDesign
Almost all other bookmark website follow similar pattern. All of them will have a URL to post bookmark followed by URL, title and any other parameters. The parameters may be optional.
Let us look at another example for technorati bookmarking. For tecnorati the posting URL is
http://www.technorati.com/faves?
There are no other parameters to pass
To come...
A PHP script to generate bookmark links