Official Libreboot X200 Guide
The X200 libreboot guide from the libreboot docs.
Official Libreboot T400 Guide
The T400 libreboot guide from the libreboot docs.
Official Libreboot T500 Guide
The T500 libreboot guide from the libreboot docs.
Legendary X200 Libreboot Guide
This guide from reddit is extremely detailed in its explanation. The guide is useful for setting up your pi for flashing, even if you have a different target than the X200 in mind
Official Libreboot Subreddit
Has useful information and updates from Leah. There are also lots of helpful lurkers (including me) who will help you out in a pinch if you get stuck.