This looked interesting: very small surface mount chips with 12 to 20 connections, containing various logic and analog components to be interconnected by programming.

They are under a dollar each, with a programmer costing $60 - with a number of sample parts included. The devices are 5V compatible, it seems. They are one-time-programmable with an in-circuit emulation mode probably using the programmer.

https://www.youtube.com/watch?v=bR0AVJ46SZ4
http://www.silego.com/buy/index.php?mai ... x&cPath=56

Internals of the GreenPak2 generation:


Because the surface mount package is not convenient, there's a project to make a DIP adapter board:


(via http://hackaday.com/2015/06/04/hackaday ... all-logic/)