The security update is recommended for all and addresses issues in bzip2, CFNetwork, Core Audio, cscope, gnuzip, Kerberos, mDNSResponder, PDFKit, PHP, Quartz Composer, samba, WebKit, and WebCore. Full details can be found here. It is available now.
The iPhone Firmware 1.01 and Safari beta 3.03 are both security updates that plug various holes in Safari. Sorry, iPhone users, no nifty new features are listed, but it will make your iPhone more secure. Apple does note that the iPhone update will not appear in Software Update on your Mac. You must sync your iPhone using iTunes to get the update. Both are available now.