In Place Editing

Use
new Ajax.InPlaceEditor('editme', './index.html');
Click me, click me!

see here
For a longer text box use:
new Ajax.InPlaceEditor('editme2', '/demoajaxreturn.html', {rows:15,cols:40});
Click me to edit this nice long text.
In place collection editor:
new Ajax.InPlaceCollectionEditor( 'tobeedited2', '_ajax_inplaceeditor_result.html', { collection: [[0,'one'],[1,'two'],[2,'three']], value: 0, ajaxOptions: {method: 'get'} //override so we can use a static for the result });
Click me NOW!.