For board members

Here's some useful stuff on what exactly a startup board does (as well as some useful info on your responsibilities as a board member). There's a little more info from Brad Feld in this Kauffman Foundation video - here's a much more in-depth and detailed video with Q&A. 

Want to understand how to make a board great? HBR wrote a great piece 15 years ago that's as applicable today as it was back then. I like the a16z podcast about being a board member from both sides of the table. If you want to be a great independent board member, there's plenty of info in here

for companies

Brad Feld's written a brilliant book on how to get the most out of your board - highly recommended. It's also worth reading the articles on his website about boards, compensation and more.  

As is usually the case, there's some great stuff from Andreessen Horowitz on picking independent board members. You'll get some great ideas on how to run an effective board (and not bored) meeting in this Quora thread. Here are some things you should absolutely avoid doing.