What's the best webinar tool out there these days?

Are there any amazing startups out there who are shaking up what's possible in the webinar space?

My company is looking for something that embeds directly into our site and scales internationally for a few hundred attendees. Live interaction and the ability to record are both musts.

If you aren't using a specific solution did you build everything out yourself? Maybe there's an open source library that can get me 3/4 of the way there? I appreciate any pointers you can offer.