Making a couple of phone calls to local electronics shops, draws me to one single option. Microchip's PIC 16F family.
So, let's go to PIC world:
http://www.grennan.com/picprog/ (Programming the PIC16F84 with LINUX)
The PIC16F84 is easily found at any electronics shops in my town. It costs around R$ 15,00 (fifteen reais), local brazilian currency, which is around US$ 8.45.
Programming PIC’s in Linux using C with SDCC
Intro to Programming PIC Microcontrollers in Linux
http://www.lancos.com/prog.html (PonyProg - GLP Serial devices programmer)
http://www.freenet.org.nz/sdcc/ (sdcc for PIC HowTo)
There is a good Spanish site about PIC projects at http://www.micropic.es/