We just released a new tool on EasyPronunciation.com. It can automatically insert stress marks into Italian words.
The database includes more than 100,000 Italian words.
For now, the tool is only available in beta version – since it doesn’t yet support the inflected verb forms.
Very soon we will update our Italian phonetic translator, so it would show the stress position in words and also differentiate between open and closed “o” and “e” sounds.