logging into network sites using one user database

Hi,

I have several wordpress installations on different domains.

Basicly i want to be able to store all my usernames, passwords and email addresses in just one of the sites databases, the networks home site.

So then i can register once on any one of the sites, but then have access to all of the sites without registering again.

I have been unable to find a plugin that allows me to do this, as i have used drupal before and they have a network sites login plugin, but i cant find anything similar for wordpress.

Any help in this matter would be greatly appreicated.

Regards!