I've been getting into opera over the last few years - the way I think of it, as my tastes in fiction and television have gone more toward the epic (Game of Thrones, Mad Men, etc) I've hungered for bigger/deeper musical experiences.

A list created in 2001 naturally misses some amazing resources. Robert Greenberg's epic "How to Listen to and Understand Opera" is a wonderful, approachable primer to the subject and is a steal for 1 Audible credit (about $15 on the cheapest plan).

Amazon Prime video has a solid collection of free video - I happily paid $25 for the version of Cosi Fon Tutte they have freely available - and you can practically find the entire operatic repertoire on YouTube. The Met Opera has a well reviewed streaming service - http://www.metopera.org/Season/On-Demand/Learn-More/.

And this is lame, but even the best Blu-Ray performance/recording can't match the experience of live opera yet. I'm actually fascinated to see if VR narrows the gap, but there's currently not anything like feeling the performers' presence, hearing the unique acoustics of a world class hall. And opera crowds, while usually greying, often add a lot to the experience - there's something about sharing the experience, like being at a movie on opening weekend.