Wippies is an OpenID service provider too
OpenID is an open, decentralised single sign-on standard, allowing users to log onto many services with the same digital identity.
Wippies provides OpenID at https://openid.wippies.com where you can sing in with your Wippies email address and your password and setup your OpenID profile and settings in the My Profile section.
The default Wippies OpenID is https://openid.wippies.com/?user=your_alias@wippies.com but Wippies OpenID also provides using your own www site as your OpenID by adding OpenID relay/delegate tags into your HTML sourcecode. This is explained on the service after you login.
I wrote a little about Wippies OpenID in Finnish to Wippies Wiki too, requires translating to other languages still.
More info about OpenID can be found on Wikipedia.
Edit: Wippies OpenID has now been removed. It was only for testing.