I think i fried it

Been playing with the arduino for a couple of weeks with some nice results. And last night everything started not to work. I cant seem to get any data from the digital or analogue pins. Im getting power but i can even get led's to blink.

I have a bad feeling that i might have sent 5v down one of the digital pins or attached GND to 5v accidentally...are there some tests i can do to figure out if ive blown some or all of the pins. Im prtety handy at surface mount soldering...is there a failsafe fuse/part i could replace? Other wise maybe if i replace the atmega...

Any advice would be helpful...