You might be a little confused here. The title says the PSP keyboard has arrived but today the news comes in the form of a homebrew application, not a USB keyboard for PSP. That's because madruscoe (also known as moneytoo from our forums) has managed to create a homebrew application which lets you make short notes and save them as .txt files on your Memory Stick using the Palm(One) Universal Wireless Keyboard.
This is the only keyboard supported at the moment and the good news is you can pick them up for around $50 on Amazon and they'll work with your Palm PDA.
As homebrew veterans will probably know, this is an amazing feat because accessory giant Logic 3 has been trying to make a keyboard for the PSP for a very long time and has failed because they needed "to acquire certain information and command protocols from Sony for the PSP" which they where unable to obtain.
There's another planned PSP Keyboard on the way for Spring 2007, but we haven't heard from the company developing the product, FITC, since August 2006. Once again, the homebrew scene has continued its habit of sticking it to the man - well done to madrusco for this release!