Possible to move the cursor word-by-word with Cmd+left/right instead of Alt+left/right?
One option would be to create ~/Library/KeyBindings/ and save this as DefaultKeyBinding.dict:

{
    "@\UF702" = moveWordBackward:;
    "@\UF703" = moveWordForward:;
    "~\UF702" = moveToBeginningOfLine:;
    "~\UF703" = moveToEndOfLine:;
    "~$\UF702" = moveToBeginningOfLineAndModifySelection:;
    "~$\UF703" = moveToEndOfLineAndModifySelection:;
}


You can't change ⇧⌘← or ⇧⌘→ though. And it doesn't work in some text views or Xcode or Firefox.

Using KeyRemap4MacBook, you could add this to private.xml:

&lt;autogen&gt;--KeyToKey-- KeyCode::CURSOR_LEFT, VK_OPTION | ModifierFlag::NONE, KeyCode::CURSOR_LEFT, VK_COMMAND&lt;/autogen&gt;
&lt;autogen&gt;--KeyToKey-- KeyCode::CURSOR_RIGHT, VK_OPTION | ModifierFlag::NONE, KeyCode::CURSOR_RIGHT, VK_COMMAND&lt;/autogen&gt;
&lt;autogen&gt;--KeyToKey-- KeyCode::CURSOR_LEFT, VK_SHIFT | VK_OPTION | ModifierFlag::NONE, KeyCode::CURSOR_LEFT, VK_SHIFT | VK_COMMAND&lt;/autogen&gt;
&lt;autogen&gt;--KeyToKey-- KeyCode::CURSOR_RIGHT, VK_SHIFT | VK_OPTION | ModifierFlag::NONE, KeyCode::CURSOR_RIGHT, VK_SHIFT | VK_COMMAND&lt;/autogen&gt;
&lt;autogen&gt;--KeyToKey-- KeyCode::CURSOR_LEFT, VK_COMMAND | ModifierFlag::NONE, KeyCode::CURSOR_LEFT, VK_OPTION&lt;/autogen&gt;
&lt;autogen&gt;--KeyToKey-- KeyCode::CURSOR_RIGHT, VK_COMMAND | ModifierFlag::NONE, KeyCode::CURSOR_RIGHT, VK_OPTION&lt;/autogen&gt;
&lt;autogen&gt;--KeyToKey-- KeyCode::CURSOR_LEFT, VK_COMMAND | VK_SHIFT | ModifierFlag::NONE, KeyCode::CURSOR_LEFT, VK_OPTION | VK_SHIFT&lt;/autogen&gt;
&lt;autogen&gt;--KeyToKey-- KeyCode::CURSOR_RIGHT, VK_COMMAND | VK_SHIFT | ModifierFlag::NONE, KeyCode::CURSOR_RIGHT, VK_OPTION | VK_SHIFT&lt;/autogen&gt;


It would make going back with ⌘← and changing tabs with ⇧⌘← stop working though.

See the source for the key code constants and predefined settings.