For the words "Filter:" etc in the drop down lists, you need to apply the last upgrade which added some langs variables to the language file General, also all templates that have drop down lists has updated you can upgdate these templates, you will need to apply these templates any way for the Arabic and RTL usage, of course you do not have to update the Frontpage template.
For all others, these are jquery plugins that you can either check the jquery sites for it to get more information on translation and customization, some quick notes, for the calender,
check the file themes/default/views/sell.js search for the line that says: datetime_picker.datetimepicker these are the configs for the calender, you can set the direction to arabic or rtl: isRTL: false, change this to isRTL: true,
these lines change the language for the calender: $.datepicker.setDefaults($.datepicker.regional['']); // [cs, de, el, es, et, fr, hu, id, it, lt, nl, ru, tr, vi] see folder js/localization
$.timepicker.setDefaults($.timepicker.regional['']);
For the html editor, it is tinymce you can check their site for details, quick note here: Edit the settings for the visual html editor in the template HtmlEditor.html in your template manager The language is set by the line:
language : "en",
you can change it to
language : "ar",
but you need to download the Arabic language files first from their site:
http://www.tinymce.com/i18n/index.php?ctrl=lang&act=download&pr_id=1 and upload these files to js/htmleditor folder
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