Can anyone recommend any good stretches for my neck and shoulders?  I sit at a PC all day and get pretty stiff.

I'd like to hear about those too.

Reach your hands up high, lace your fingers, and push up - that will loosen up a lot.  Shrugging your shoulders will also have positive effects - bring them up towards your ears, then circle them around.

I get up and walk around, go to the loo, stretch my back out a bit.  it wakes me up too!

I have a sore back - i have to go to the loo and do that stretch where you put your foot up and lean forwards - the sink counter is the perfect height!