Need single sing on solution?

Hi All,
I am doing my site user authentication through LDAP server and my
company has 3 more sites with different technologies and they are also
doing user authentication through LDAP server.
Now we want that when user logged in my application then
user also logged in other application and
Please help me out.
I will be so thankful to all of you?

If u r saying bout session or cookies please give some code example or
detailed description.

Thanks & Regards,
Varun G.