This electret microphone module is a high-quality amplifier. It has a single/dual input of 20dB. This is useful in recording sounds, applicable to portable audio devices such as laptops, cell phones, and handheld computers.
This small mono amplifier is surprisingly powerful - it can deliver 3.2 watts of power to a 4 ohm impedance speaker (5V power @ 10% THD). Inside the miniature chip is a Class D controller, capable of running from 2.7V to 5.5VDC. Since the amp is a class D, it's incredibly efficient - making it perfect for portable and battery-powered projects.
MAX31865 RTD Platinum Resistance Temperature Detector PT100 to PT1000
This slim little board has a class D amplifier onboard that can drive 2 channels of 4-8 ohm impedance speakers at 20W each.
FeatherWing Adafruit Music Maker is an enhanced version of the other FeafWing Adafruit products because it has a 3W amplifier integrated. This includes the VS1053, a coding / decoding chip that can decode a wide range of audio formats such as MP3, AAC, Ogg Vorbis, WMA, MIDI, FLAC, and WAV (PCM and ADPCM).
TPA6120 High Fidelity Stereo Headphone Amplifier Module
PJRC Shield with Audio Amplifier, Flash Memory and Led Driver for 3.2 Teensy and Teensy-LC
High gain audio amplifier based on the LM386 integrated circuit.