(i.e., things I have found helpful)
If you're interested in applying to PhD programs...
I highly recommend checking out the Business PhD Wiki, which contains several resources, like examples of personal statements and CVs: https://businessphdwiki.com/doku.php
If you're from an underrepresented background and wanting to learn more about business academia, consider the Introduction to Diversity in Doctoral Education and Scholarship (IDDEAS) Program, which is a fully-funded, two-day program that introduces undergraduates to the field of business academia. Applications open up each November! https://doctoral.wharton.upenn.edu/iddeas/
If you're wondering how to navigate a PhD...
Calarco, J. M. A Field Guide to Grad School: Uncovering the Hidden Curriculum. https://press.princeton.edu/books/paperback/9780691201092/a-field-guide-to-grad-school
Science's Letters to Young Scientists series: https://www.science.org/topic/careers-overline/letters-young-scientists
Harvard Business Review's "Time Poor and Unhappy" Big Idea series: https://hbr.org/2019/01/time-for-happiness?ab=seriesnav-bigidea
If you're from an underrepresented background, I've only ever heard glowing reviews about the PhD Project! https://phdproject.org/