Singers will feel right at home here! Who wrote that aria? What opera is it in? Who wrote the libretto? Are there recordings? The Aria Database is a free resource to help you.
Staff and students at the Royal Conservatoire of Scotland will probably be very familiar with IPA Source, which gives you transliterations, phonetic pronunciations and so on. It's fabulous, but our subscription is only available on campus. Therefore, The Aria Database might be a useful fallback for those away-days when you need aria information in a hurry.