My favourite channel right now is PhilosophyTube, Oliver's a great dude. Honourable mentions are other leftist youtubers like halim alrah and azureScapegoat :]
i like philosophytube.. for the last 6 months or so i've been sensing the channel undergoing some noticable.. . *ahem*... . changes, but they haven't made any official statements/acknowledgements, so i guess i probably shouldn't get out over my skis.. other channels PT fans might like (for those that haven't seen them already) is hbomberguy (although he sometimes dials it up to 11 for "comedy", which many might find annoying) and foldingideas..
my personal favorite lately has been jenny nicholson.. she's not all that political really (or at least her channel isn't explicitly about that), and she kind of gained widerspread traction for being a fan of 'stars wars' (which i personally don't give a single f#@k about), but her topics are diverse and her smart/dry sense of humor kind of make her feel like the cool best friend you're always happy to see (or at least i am)..