Is there a Command + ` equivalent (cycle through windows)?
Alt - ` and Shift+Alt+` do this by default.
The desktop will map whatever key is above the tab key to do this, on US keyboards it's the ` key.
- What are Unity's keyboard and mouse shortcuts?
In Xfce you can use Super + Tab (super is the "Windows" key on Microsoft keyboards). Not sure if this works in other window managers.
In Ubuntu 12.04, by default, Super+above tab does this.
Alt+ Window Number.
For example Alt+1 for first window. Alt+2 for second window etc...
In firefox and chrome you can also use Ctrl+Tab