It was a depressing experience, but I finally worked out how to use the t-online international access (Einwahl) from my San Jose hotel room.
First, I had to get the phone numbers. Over at Spicy Noodles, André has a link to a list of them.
Then, I had to guess on how to create the ipass account phrase. It looks like this:
Now, enter this information in the PPP tab of the Mac OS X network control panel and connect.
If you need more information, send me a mail.