It's definitely one of my favourite places to collect reference, inspiration and tutorials, especially because you can share a board with other people so easily.
I have boards for all sorts of things; art tutorials, fashion ideas for characters, inspiration and reference for painting my minis, ideas for what sort of suit I want to wear at my wedding.... and, the most important board of all... I have a board where I collect pictures and videos of adorable animals to look at when I'm feeling stressed.
Overall, I find it a really great resource for all sorts of things, particularly pinning down a specific aesthetic, because it'll find you a bunch of similar things, and you can go through getting more specific.