Sony America's released the 2.01 security update for PSP through its Software Update page. The update closes a loophole that allowed hackers to downgrade PSPs to older firmware and run homemade programs like emulators on them.
And, as far as we can work out, that's all it does. Sony's official site cunningly claims that 2.01's responsible for the various additions made to 2.00 - including a web browser, better movie playback support and more languages - but they're probably not fooling anybody.
However, if you're keen to remain fully up to date, that's where you go, and full instructions can be found on the site. We've yet to find out where you can grab it from Sony Europe, but we'd imagine we'll be told in due course.