FYI: Apple + ~ works to switch between open windows of the active application, whether it be Safari or any other app.
Also, in Safari, you can switch between tabs using command-shift-left/right arrow (in Panther) or command-shift-[ or ] in Tiger. The first method works in Tiger as well as long as you're not in a text field or a blank tab.
MBP C2D 2.2/120GB/2GB (10.5.0)
G4 1.42 mini 80GB/1024/Combo/AP/BT (10.4.10); 20" ACD; miniStack+300GB; iSight; AirPort Express
G3 600 iBook 30GB/640/DVD-ROM/AP (10.4.10)
4G iPod (40GB) | 2G iPod nano (4 GB-red) | My Mac blog: Singing the Apple