The Incomparable MadLetter has created 2e-style Charm Cascades for Solar, Dragon-Blooded, and Lunar Charms, as well as the Martial Arts styles in the core book.
Combat flowchart by GivenFlesh
Social system cheat sheet by Redthorn
Another social cheat sheet, creator unknown
Interactive PDF Sheet by MrGone (Click on 'other sheets' in the sidebar to access)
Master Sheet (Google Docs spreadsheet)
Advanced Character Generator by Refhi (Excel/LibreOffice spreadsheet)
Familiar Generator also by Refhi (Excel/LibreOffice spreadsheet)
Battlegroup stat generator (Online app)
Wise Artificer's Insight, a Solar crafting calculator
"Useful Links" thread on the official forums
Dragon-Blooded: What Fire Has Wrought
Hundred Devils Night Parade: Collection or Individual parts
Adversaries of the Righteous: Collection or Individual parts
Tomb of Dreams (Adventure module)
These are referral links. The developer of Lot-Casting Atemi will receive a referral credit for any content you purchase after following one of them.