As part of the new iPad announcement Apple released new versions of iPhoto and GarageBand for iOS, but in addition Apple updated the existing versions of these programs for its Mac OS X platform.
The update for iPhoto is fairly sizable at 354.57MB, which may seem a bit strange given that its only new feature is the ability to delete photos from the iCloud Photo Stream (a feature that Apple also included in iOS 5.1); however, the update does also include fixes and enhancements included in the previous 9.2.0 update, such as problems with rebuilding libraries, compatibility with iCloud, and refinements to importing, gesture support, and printing problems.
iPhoto 9.2.2 is a recommended update, especially if you use the iCloud photo stream, and it will require OS X 10.6.8 or OS X 10.7.3 or later to install, meaning that if you have either Lion or Snow Leopard installed, then you will first need to update it to the latest version before applying this update.
On the other hand, the GarageBand update's system requirements suggest it only requires OS X 10.6.8 or later to install. The update is also smaller at 47.61MB and includes fixes to improve compatibility with GarageBand for iOS, fixes cases in which software instrument notes get stuck, and corrects some problems with the lesson videos feature of the program.
Both of these updates are available via Software Update, but can also be manually downloaded and installed from their respective update Web pages (iPhoto, GarageBand). As always, be sure you fully back up your system before applying these updates. While they should not cause any problems, Updates to programs that handle data libraries, such as Aperture, iPhoto, and iTunes, have at times resulted in problems accessing the library data. Any time you update software, there's a chance something might go awry; being able to restore your system or data if needed is recommended.