Zilog (inventor of the famous Z80 microprocessor chip) has updated versions of the Z80 in microcontroller form, and also updated versions of the even older Z8 architecture. Both have flash memory and some interesting peripherals , and inexpensive "evaluation boards" that include a C compiler. At one time, the zilog evaluation boards were quite "full" compared to many low cost evaluation boards, but the current versions seem less so. (My EZ8kit has 4 5x7 matrix displays, an IRDA transceiver, two rs232 async ports, an rs485 port, and assorted buttons and lights. IIRC, it was $50 (special deal at a trade show.))
said in comments:
Most of the people who have commented list the PIC, PICAxe, ARM, 8052, or Basic Stamps. These are all popular chips, but if you are just getting started with microcontrollers, you might want to start with something fairly cheap. How does $40 sound?
That's what the Zilog Z8 Encore! 8-bit microcontroller development kit costs. The Z8 Encore! microcontrollers are available with 1K to 64K of flash RAM. For speed, they operate at 5- to 20-MHz, and depending on the chip, they are available in various packages from 8 to 80 pins. The $39.95 development kit contains a development board with input/output pins, a wall wart power supply, computer cable (USB or serial to connect your computer to the development board), and a free C compiler and assembler that runs under Windows. You don't need to buy or build a programmer, since you can program the chip right in the circuit you've built -- without having to remove it and reprogram it in a programmer.
All the Encore! chips can communicate serially through a UART (some have 2 UARTs). Some have analog-to-digital converters built-in, and some have an infra-red (IRDA) communications port. Oh, and there are up to 4 built-in timers on the chip, depending on the chip version. The price of an Encore! microcontroller is pretty reasonable, given all the capabilities (anywhere from $3 to $13 each from Digi-Key).
The C compiler is excellent. The Zilog C compiler has most of the capabilities of "big boy" compilers, like a floating point library, trig functions, etc. It produces better assembly code than I can, so I use it almost exclusively.
Remember that almost any non-trivial code you write will have bugs. The debugger supplied with the development kit permits you to step through your code and look at the results of variables stored in the various registers to help you locate your mistakes.
Digi-Key stocks two different Encore! development kits (either one costs $39.95); one for 8K/4K chips, and the other for 16K through 64K chips. The Digi-Key part number for the 8K/4K development kit is 269-3183-ND, and the part number for the 64K development kit is 2693249-ND. http://www.digikey.com
has a large number of sample applications, full documentation of their microcontrollers, and free updates to the C compiler supplied with the development kit.
I'd say that the only downside is that the Z8 Encore! isn't as popular as the PIC as a hobbyist chip, so there haven't been any books or many of projects published for it except for some articles in Circuit Cellar magazine. Oh, and if you are interested in microcontrollers, Circuit Cellar and Nuts & Volts magazines are two that cover the subject. Both are available at Barnes & Noble bookstores -- maybe Borders too. Or, just go directly to their websites:
Circuit Cellar Magazine
Nuts & Volts Magazine