Motorola:

Started playing with the 6809 in the early 80's, built a Micro computer system based on this micro. There was a user group that produced PCB's for this device on a S50 bus, The 6809 machine probably still goes(but was retired when the IBM PC XT clone came along), it is stored in the basement with all the other old (valuable) junk!

The 68HC11A1was a very cheap option, (free when you extract them off used IDE HDD controllers on older 40MB connor Hard drives). They have 512 bytes of on board EEPROM, which with a bit of assembler could perform simple tasks, e.g. read the analog inputs and transmit the result out the SCI.
To program the beast you wrote assembler using notepad or similar, produced a hex file using one of many assemblers available, then you downloaded hex file to the chip using PC-Bug. (this is a very brief explanation)
It is hard now to come across the older scrap hardware with these devices on, with a chip ID that is meaningfull. Motorola produce a lot of these chips with cusom numbers on for the particular client that purchased them.

MICROCHIP PIC:

(16F84), PIC basic Pro: This is really great to produce a quick result, have used the Dontronics sim stick(DT101) to quickly produce serial controllers. Disadvantages: It lacks simple Interrupt functionality (my opinion), and has no real string capability. That aside, it has great support, and continued development improving it. Sample Code.

ATMEL AVR(90S2313) BASCOM-AVR:

I have looked at the BASCOM-AVR Basic as a means to overcome the disadvantages in PIC Basic Pro, but it lacks other features of PIC Basic Pro that I like (sigh) AVR_Code.htm Well when it comes down to choosing, its the device / programming tool with the appropriate functionality for the job (at the lowest cost)! Sample Code.