Apple has released updates to iTunes 9.2.1 and iBooks 1.1.1 today.
iTunes 9.2.1, available for Mac OS X and Windows PCs, is mostly a maintenance update that addresses bug fixes, performance issues, and will disable "older versions of some incompatible third-party [iTunes] plug-ins."
I don't use any plug-ins with iTunes, but if you do, you'll want to double-check yours for iTunes 9.2.1 compatibility before applying this update.
iTunes 9.2.1 is available for download on Mac OS X and Windows PCs from the Apple Software Update control panel.
iBooks 1.1.1 for iPad, iOS 4 Devices
The iBooks update adds some nice features to Apple's ebook reader. This update includes improved support for books and PDF files with images and adds support for books and documents with audio and video content, as well as additional performance tweaks and bug fixes.
You can download the iBooks update directly to your iPad or iOS 4 device by using App Store on the device or by downloading the update from iTunes and syncing it over to your iPad, iPhone, or iPod touch.