Most of the video interviews we have set-up to-date have been on Skype. It's free and easy to use on either your PC or Smart Phone. Even if you don't have a pending interview, it's a good idea to go ahead and set-up an account so you are ready when it comes. (include it in your LinkedIn profile contact info too)
HireVue is different from the live video interview in that you record video responses to a set of questions. We see this used most often in international settings where time zone differences and remote locations make it difficult to arrange live interviews. Even though you don't get the live interaction, there are a few advantages to this system:
Dress like you would for an in-person interview. Even though you're not really face-to-face, because it is visual, the interviewer is judging your appearance just the same.
Choose a suitable location for the call that is free of distractions and background noise. You also want to ensure that the lighting is good - too dark or too light can make a negative impression even if it isn't a conscious one. Test your video and audio settings in advance.
Test your connection speed (especially if you're using a cell phone), video and audio settings in advance. Most webcams are HD quality today so make sure you allow for an appropriate distance from the camera (they don't need to be able to count the pores on your nose).