Sure, many of us have.
You can see a bunch of examples of arduino-like boards here
http://www.crossroadsfencing.com/BobuinoRev17/
PCB, $3.40 each in lots of 10 - 54mm x 69mm. Or you can wire it up discretely on a piece of perfboard.
ATMega328P-PU
10K resistor
anti-latch up diode (such as 1N4148)
16 MHz xtal
22 pF caps
100nF caps
DC power connector
reverse polarity protection diode (such as 1N4158)
USB connector
PTC polyfuse
6 pin female header
8 pin female headers
FT232RL chip (or a FTDI module, or a CP2102 module)
2x3 icsp header
reset switch
5v regulator
47uF caps
4 LEDs
4 1K resistors
leaves out the autopower switching parts
Price it up, see what you get. dipmicro.com has good prices on almost all the parts.
Some things are only available in surface mount, such as the polyfuse.
If you want a minimal component board (no USB interface) you can build up this board
http://www.nkcelectronics.com/arduino-runtime-board-rev-b.html