The iOS 6.1.1 is now available for iPhone 4S only and this requires you to jailbreak your iPhone again. Although, the first evasi0n jailbreak will not work on this new iOS version, but don't fear!
I'll tell you how to jailbreak your iPhone 4S.
Download evasi0n 1.3
Mac OS X: mediafire.com/?dx10n5cmld3h585
The process is exactly the same as the previous one (in case you had your iPhone jailbroken before iOS 6.1.1 was released).
Step 1: Download evasi0n and open it.
Step 2: Connect your iPhone.
Step 3: Click Jailbreak. The process will begin automatically.
Step 4: At a certain point of the process, evasi0n will ask you to tap a new jailbreak icon that was installed on your iPhone. Once you tap it the process will continue. Please note that your iPhone might reboot before evasi0n asks you to tap that icon.
Step 5: Wait for evasi0n to finish the process.
Step 6: When the process finishes, Cydia will be installed on your iPhone.
If you want this tutorial with images, you can check this one. It's exactly the same process, although make sure you're using the file you downloaded on this tutorial and not on the one I mentioned above.