Do either the Canon PowerShot SD880 IS or the S100 have anti-aliasing filters? If so, has Canon announced any P&S model(s) without OLPFs?
Not as of 2013.
Canon is a bit late to the game. Nikon, Olympus, Pentax, and Fuji for example make various cameras without optical low-pass filters.
It is quite a new development for a variety of reasons, most of which have been covered in existing questions/answers on this site. Take a look at: