Is there a Ctrl + Tab equivalent on Mac OS X?

Command + ` (the ~ key) works with many programs.

Depends on the application but most of them support:

• Command + Shift + [

• Command + Shift + ]

for switching between tabs.

There is a piece of shareware called Witch that emulates Windows alt+tab. It shows all windows in all applications, sorted by application. It costs €9.95.