Apple has released Java for Mac OS X 10.5 Update 7 for Leopard users, updating Mac OS X's J2SE 5.0 to version 1.5.0_24 and Java SE 6 to 1.6.0_20 and delivering "improved reliability, security, and compatibility for J2SE 5.0 and Java SE 6." The only details given revolve around security fixes, so it's probably worth downloading this update even if you don't anticipate using Java applets much. Also note that J2SE 1.4.2 is no longer being updated and remains disabled in this update, which requires Mac OS X 10.5.8. (Free, 122 MB)
Copy Disk Image as Folder
When you open a .dmg file, a disk image is mounted. You are then generally supposed to copy the contents of that disk image to your hard drive (to your Desktop, your Applications folder, or wherever). But what if you want to copy the whole disk image, including all its contents, as a folder? Hold the Option key, and drag the "proxy icon" in the title bar of the disk image window to the destination in the Finder.