History

There are few inaccurate histories of the 555 timer invention on the web so a good source is from the designer himself, e.g., http://semiconductormuseum.com/Transistors/LectureHall/Camenzind/Camenzi...

He also wrote several interesting books. The history and detailed design considerations are covered in a book he kindly made available as a PDF file before his death in 2012: http://www.designinganalogchips.com/_count/designinganalogchips.pdf

Circuits

This is a reasonable compendium of interesting circuits using the IC: http://www.555-timer-circuits.com

Some more:

http://www.nutsvolts.com/magazine/article/using-the-555-timer-ic-in-spec...

Radio Circuits

AM Receiver

https://hackaday.com/2011/02/25/hear-that-its-a-555-timer-am-radio/

AM transmitter

http://www.circuitsgallery.com/2013/08/555-AM-transmitter-circuit.html

FM

http://streampowers.blogspot.com/2013/07/using-555-as-fm-transmitter-cir...

Audio Circuits

VCO

High Performance VCO : http://www.electro-music.com/forum/topic-54623.html DRAWDIO

https://www.adafruit.com/product/124

ATARI PUNK CONSOLE http://www.synthrotek.com/products/lo-fi-synthesizer-circuits/atari-punk...

Variations

The CMOS versions of the 555 timer are interesting and lend themselves well to low voltage e-textile applications. My favorite variant is this one: https://www.jameco.com/z/CSS555-ID-Custom-Silicon-Solutions-CSS555-Micro...

Here is the largest variant I know of: https://shop.evilmadscientist.com/productsmenu/tinykitlist/652-555kit

and the smallest (a 1mm x 1mm) package:

http://www.ti.com/product/LMC555/samplebuy https://www.mouser.com/Semiconductors/Integrated-Circuits-ICs/Clock-Time...