WikiCFP is a useful wiki site that collates CFP.
However am a bit disappointed that it does not automatically track to the following year for the same events, e.g. once a conference is over and the dates for the following year announced, it should link to the following years conference details, instead of manually searching for it.
There is also an iPhone Application called WikiCFP that links to the site. Although functional, the application is not very intuitive, for the relatively high price of the application I was expecting more out of it, e.g. calendar integration, etc.