Does showcasing pet projects on my personal blog compensate for not having references?
No, realistically a list of external projects will not make up for not having letters.

Letters are typically not, or not primarily, used as a description of projects you have done, but as a subjective evaluation of your potential as a PhD graduate student. Letters may include a discussion of undergraduate research, but will also include a discussion of your personality, especially your strengths and weaknesses as a researcher. It is evident that this cannot be learned from a description of projects alone, especially given that this list is curated by yourself.

Incidentally, this is also the reason why senior professors are considered the "best" references - admission committees assume that the best judge of prospective grad students are those you have seen many grad students succeed and fail, i.e., senior professors.

Edit: as jvb correctly notes, the question is about master rather than PhD applications, but at least for a master by research, this does not change the spirit of my answer. For masters by coursework, I think most universities don't really employ a competitive selection procedure anyway (at least the ones I know don't).