In an interview situation the best way to sign off is to try and lead from the subject matter to the end of the video smoothly.
In a lecture the best way is to finish is the same way the speaker would end a normal lecture. Something along the lines of "Well that's it guys, if you want to get a copy of the slides you can download them at  and be sure to subscribe to my posts on Twitter". Then proceed with the standard call to action and the company logo.
"This is Adam Cogan signing off until next time" (grins at camera with a thumbs up)
Figure: Bad example – impersonal, cheesy and uninformative sign off
Figure: Good example – personal, the speakers relate to each other well, refers to subject matter in the video
Figure: Good example - See Richard Campbell do it perfectly 10 seconds from the end of this video
"Well that’s all great stuff Joe and we're looking forward to seeing your new software soon"