On the Mail.app update, some users may experience issues with Mail after updating to 10.5.6. If so, run Software Update and you should see the fix. Otherwise, you can download it directly from Apple.
Searching for contacts in a large address book (more than 1000 contacts) is faster and no longer results in a “slow script” browser alert message
Exported vCards with multi-line addresses or notes can now be imported into the Mac OS X Address Book
Adds keyboard shortcut to create a new contact
Additional formatting options for European phone numbers are now supported
Calendar
Adds sorting of To Do items by calendar or title
Long event titles now appear properly in Month view
Gallery
Updated “Tell a friend” email message
Resolves an issue related to setting a new album’s key photo
iDisk
Files and folder names that contain Japanese language characters now display properly on the web
Account
Hosting of iWeb pages can be configured for personal domains ending in “.eu”, “.ax”, “.tl”, “.gw”, “.kp”, “.rs” or “.su”
Family Member accounts now display the accurate renewal/expiration date
Resolves an issue that prevented some members from using an activation key (MobileMe box) to renew a subscription
Login
“Keep me logged in for two weeks” checkbox now works reliably