For those who are not familiar with Niconicodouga, it is a Japanese video sharing site with a commenting system that is displayed streaming across the video (Can be annoying when spam rolls around but there is an option to turn off comments). An account is require to view the videos so for those who are not proficient with the Japanese language, there are an abundence of guides on the net: Found in one google search.
If you're uncomfortable with Niconico, most videos are also reuploaded on Youtube so do not worry! New to Vocaloids? I suggest Youtubing the following artists: Supercell, Sasakure.UK, CosMos bousouP, Hachi, Deco*27, and 40mP.
Not interested? Well I'm sorry to hear that, but do stick around!