Current Capacity
Trace Width Calculator: https://www.4pcb.com/trace-width-calculator.html
Handy calculator for figuring out PCB trace widths based on current and temperature requirements.
Wire Gauge Ampacity Table:https://www.powerstream.com/Wire_Size.htm
Useful for getting a sense of what current load different wire gauges can handle. Note that the ampacity table in the competition rulebooks should always be deferred to whenever possible.
LC Filter design
LC Filter calculator: https://rf-tools.com/lc-filter/
Enter filter topology, order, input/output impedance, cutoff frequencies, and ripple requirements
Outputs the either the exact or the nearest standard component values needed to implement the filter, along with a schematic of the filter and a bode plot of the frequency response
Switching Power Supply Filter Design app notes: https://www.ti.com/lit/an/snva538/snva538.pdf (edited)
Section on parallel damped filter is a good reference on how to use damping resistors to eliminate resonance from a passive LC filter
Textbooks
https://drive.google.com/file/d/12sun2JBasXaoNDLZOBjQRBu2lIeI1aFa/view?usp=sharing
The textbook for Electronic Design, one of the better texts on electronics fundamentals
https://drive.google.com/file/d/1wlQD3nnpW5N2x0rdbe7Yf297_CyEb_g2/view?usp=sharing
The textbook for Power Electronics, very good intro text for power electronics
https://drive.google.com/file/d/1SNHvNBDIcWseuGaRUFVAuoEPjc1r7Bfm/view?usp=sharing
A fairly comprehensive overview of practically every kind of sensor