volunteer visa? (Schengen Countries)

Hello all.  I have a plan to visit Europe this fall, winter, and spring; hopefully volunteering through Helpx.  I was hoping to visit Portugal, Spain, France, Italy, and Greece over 5 months but it seems these are all schengen countries and apparently the limit may be 90 days for tourists.  I'm from the United States so I don't think I need a visa to visit for these 90 days but it could cut my trip short by two months, or I'd have to go somewhere else before coming back. 

Also, does anyone have experience working for cash or making money while helpxing or wwoofing?  Hopefully not too off topic but it's interesting nonetheless.  20 or 30 hours per week still leaves plenty of time to do more, if I'm not in the mood to do my own thing.

Does anyone have experience crossing borders, particularly schengen countries, to do these activities?  Do you just lie and say you're a tourist?  Or do you tell them you're volunteering/workiing?  Do you need a "work" visa to do volunteer work?  I'm checking the web sites I can find but so far have found no clear answers.

Thanks!

There is a so called "D Visa" for staying in the Schengen Zone more than 3 months.  For instance:
http://www.consulfrance-chicago.org/spip.php?article482

Also, I know that at least in the Czech Republic and Slovakia you are supposed to register where you are staying with the foreign police if your stay will be more than a few days.

thanks for the link

Welcome to come and help do what you want here, mostly natural DIY I would say... instead of going through any systems (though some disclaimers are good and asking some basic questions helps)/
If you want to come to Czech Rep (it's in Europe!)... Anyway check out my links below and happy to talk a little money or showering you with excess of what we have...

First of all, I appologize for cross posting in the European Section.  I'm planning on travelling Portugal, Spain, France, Italy and Greece over 5 months.  Does anyone understand the implications for a U.S. citizen trying to do this?  It seems my limits for a tourist pass are 90 days, 2 months short, and possibly more since I'm contemplating sticking around there with the high coast of boat travel and my aversion to planes(which aren't cheap either). 

Has anyone jumped around the schengen countries?  Is 90 days a country limit or a collective country limit?  When you enter countries to WWOOF or HelpX, do you tell them you're just a tourist, or do you tell them your intention to work in exchange for food/shelter?  Can you get by on a "vacation" or do you need a "working" visa?

I know this varies between all countries and countries of origin.  I'm particularly interested in the schengen countries but someday would like to travel in other regions so I'm interested in any advice regardless of region.  Thank you!

dont mention the word 'work'!!! even if its unpaid - as soon as you say it, your fate will be doomed!. I have loads fo volunteers from the US - they all come on tourist visas and just go in and out of the Schengen countries to extend their stay time.
good luck

kathy
www.stjamespark.biz