Nathan Carter’s Visual Group Theory textbook PDF (free access with UConn login) and errata
Judson online textbook including Sage exercises in English and Spanish
Interactive online course on transformations and symmetry
Wikiversity Intro to group theory
Dana Ernst’s open-source inquiry based Abstract Algebra
Keith Conrad’s expository papers (many are on algebra)
Matt Macauley’s Algebra class at Clemson (with commercial-free lecture videos recorded in 2010)
Podcasts which go along with the chapters in Visual Group Theory textbook
Advice on Mathematica Writing by Keith Conrad
Some Guidelines for Good Mathematical Writing by Francis Su
Examples of proofs by induction by K. Conrad
Group Think by Steven Strogatz
A simple visual editor for writing diagrams and converting it to Tikz github.com/yishn/tikzcd-editor, try it out at https://tikzcd.yichuanshen.de
Joseph Gallian’s website containing many resources related to his textbook
Math students, connect with prospective employers here: MAA Career Resource Center
Use CamScanner app or another scan app to scan your hand-written homework into PDF.