Ist it possible to see the settings of my known WLANs stored on my iPhone? I only know that I can access the settings of the current network when I am logged into one.
Edit: The iPhone is not jailbroken and I do not intend to jailbreak it.
As mentioned by others, jailbreaking is the easiest way. But if you really don't want to, you can back up the iPhone and use a tool like Backup Extractor to view the .db file that stores the settings.
No you can't, unless you jailbreak.
However, jailbreaking is now so easy and painless that there really is little reason not to do it. For example, just follow this guide if you're on iOS 5.1.1.
After you jailbreak, you'll be able get apps like "WiFi Passwords" in Cydia which do what you want.