Oscilloscopes

Used to visualize and measure waveforms
EE 206, ECE 311, 320, 321, 376, 401, 403, 405

Free!

Cell phone app.
​Output the signal to a speaker through an 8-Ohm speaker.  Use PianoTuner (free app) to measure the frequency

$34: Microfun

Available on Amazon and ebay.
Search "pocket oscilloscope". Max frequency is about 200kHz.

$159: YeaPook

Recommended  I just got one and I really really like it.  Screen capture, USB interface.  Has no problems with 300ns pulses. Available on Amazon and ebay.  Search "pocket oscilloscope"

Multimeters

Used to measure voltage, resistance, transistor gains, etc.
EE 206, ECE 311, 320, 321, 376, 401, 403, 405

$15: Annmeter

What I've been using for the past 10 years - does everything I need.  Good price too.

$16: NeoTek

For one dollar more, you get alligator clips but lose the temperature sensor

$30 Lovum

Amazon choice and top seller