Engadget is reporting that Madcatz will be releasing a mini-QWERTY attachment, similar to the one announced for the Xbox 360, for the PS3. The design is a bit different (i.e., flawed) as it connects to the SIXAXIS controller from the top rather than on the bottom as well as looking a bit cramped with the keys awfully close to one another.
Sony has not yet announced an official peripheral for the PS3 so it seems that the Madcatz attachment is your only choice for a mini-keyboard.
For those of you who don’t wish carpal-tunnel syndrome upon yourself the PS3 also allows you to connect a full sized wireless keyboard via bluetooth.