SmartTag Maker will allow you to encode regular NFC tags to behave like Sony Xperia SmartTags. This allows a lot more options in terms of form factor, stickers, bracelets etc. Perfect for if you have a Sony Xperia S.
Note: You will need the app Xperia SmartTags installed to use your new tags.
Check out my other apps for things to do with your shiny new tags, specifically Car Mode On.
This app is in no way affiliated with Sony, I just really like their products.
On a related note, while I am in no way affiliated with www.rapidnfc.com, I have had nothing but good experiences as a customer.
1.2 A nice man from NXP.com asked me to stop using his icon
Then their support team offered me a very similar one I could use, no problems.
Then the nice man from NXP told me I couldn't.
End result, the wait for tag screen has changed (for the better IMHO)
1.1 Support added for the newly announced NT2 tags. This adds orange, green, purple and gray tags. You must be running Smart Connect for your phone to recognize these.