I use wallwarts in many projects, no onboard regulator. Need a DC source anyway, why not start with the right voltage?
Thru hole connector
http://www.mpja.com/prodinfo.asp?number=18549+PL
Switching DC Wall Power Adapter 5V / 1A - dipmicro electronics 1A
Switching DC Wall Power Adapter 5V / 2A - dipmicro electronics 2A
5V 4A Power Adapter OPENPEAK OP-20004 4A
328's are spec'ed to work at 16 MHz down to ~3.8V
