For all of you, that want to check mails or do anything else online, while in Erfurt, just go to the Coffeeshop Company.
The coffee bar on the Wenigemarkt supplies a charge-free wirelessLAN hot spot for private usage. The only thing you need to bring is your own laptop.
Just order an moccacino, latte machiato, something to eat or anything in between and just ask the the waiter for the WEP Key or try some words, with the leghts of 5 characters, out of the menu – I am sure you will find out.