There's some evidence from the medical community that green lowers blood pressure and has a calming effect on patients. That's why you'll often find hospital walls covered in the stuff.

So, if you're looking to induce a similar experience amongst web site visitors then go for it, otherwise I would suggest leaving it to the hospitals.

I guess it comes down to whether you're designing a website for yourself (so are choosing a colour you like) or designing for others (choose a colour to invoke a reaction).

Personally I find the colour green to be the leader of the bland.