After upgrading to Lion, all my 802.1X configurations are gone. There also does not seem to be a possibility to configure them via the system preferences:
It just tells me to get a configuration file from my system administrator.
How can I create a profile manually like before, or, if this is not possible, can I create a configuration file myself with the data I have and how?
It turned out that it was sufficient to just provide my credentials at the when I connected to the network. I was just confused as there was not profile anymore in the preferences as you can see in the screenshot above. I hope the accepted answer will still be useful.