Ask HN: Where can I find prebuilt, trainable machine learning models?

I am very interested in ML and am looking into tutorials etc. In the meantime, however, I have an idea for an application that would analyse and detect basic images (don't want to give it away of course ;)). So I was wondering if there are any untrained models that I could train with my own dataset (I have an absolutely massive training dataset available so that isn't an issue) or some kind of tutorial/s that could get me going in the right direction. Thanks for any help.