Which countries require documentation of health insurance? This is news to me.
Certainly there is travel health insurance such as TravelGuard and Access America.
I only ever did this once, didn’t bother with it last the last two trips, but I suppose different circumstances dictate different preparations.

I have never been asked for proof of insurance on any trips.  The only thing they ever ask is how long is my stay, even then they don’t ask to see my return ticket. 
 
You can certainly buy travel insurance for the duration of your trip, I only did it once many trips ago. 
 
If you are a student, check if you already have some sort of insurance through your school.  I know that when I was a student, our student fee included some sort of health insurance coverage.

So far, I’ve found that it is required for entry by Slovakia and Latvia. I haven’t looked into it with Slovakia, but for Latvia it says that they literally stop you at the border to check that you have it, and can be fined for not having it within the country.
 
I know it isn’t included with my school tuition because I don’t go to main campus, and if you want it you have to pay extra. Any idea how much travel insurance for one month would be?

My school was sort of evil that way. It was in the student fee (not the tuition), they made us pay for all sort of crap we don’t need (if you don’t want it, you have to opt out), such that our students fees were one of the highest in the country.. ah good times.

If you live near a big enough school, STA (also known as council travel) should have the travel insurance info. 

http://www.statravel.com/cps/rde/xchg/us_division_web_live/hs.xsl/travelinsurance.htm

I also recall seeing brochures for it at the airport.

I was never asked for proof of insurance upon entering Latvia. I flew in. I remember reading on some message board that somebody was asked for proof when entering Lithuania. Had suprised me because I wasn’t asked when I entered the country.

I think I might just skip Latvia on this trip anyway :-/ I’m still in the “whittling” process, trying to figure out where I can go and what I DEFINITELY have to do, and whatnot. Maybe one day it’ll be covered by Eurail That’s actually one of the bigger concerns; I already am going to make one definite excursion outside the realm of the Globalpass, to Slovenia; I’m probably going to make a day trip to Tallinn from Helsinki too, which is what got me thinking about going a little further south to Latvia. All told, I probably want to go to Latvia more than Estonia, but Estonia is just so damn convenient to get to
 
I just don’t want to fall into that rut of trying to see EVERYTHING in one month, and then not enjoying any of it. It seems every day I learn about something new I want to go see, so I’m just worried about stretching too thin, I suppose.

For the record, EVERY EU MEMBER STATE (including Latvia, Lithuania, France, Germany, you name it) requires medical insurance. The fact that normally they don’t check your policy at the border does not mean you should not have it. A US citizen under 29 y/o can get one month of medical coverage valid anywhere outside the US or Canada for $32 from www.IMGlobal.com and that seems to be a very small price to pay compared to what typical domestic US insurance costs.

Wow, really? I had no idea. Maybe the other’s just aren’t strict about it, because they don’t even mention it on the travel.us.gov site (or whatever… the one with the travel advisories) for any countries except Slovakia and Latvia (well out of the ones I checked anyway… only checked ones I’d be interested in going to hehe)
 
Thanks for the heads up though.

Denmark have free emergency care for visitors. I speak from experience…. (By the way, the US does too—for everyone—but that’s probably a Pub topic).

Thanks Seva.
I guess we simply were never asked (and we do have health insurance, though I am not sure how covered we’ve been while traveling.)
My kid once had a cut finger stitched up in Nice, and I don’t think he was asked for payment, let alone proof of insurance.

Well, I guess this is a sort of a gray area. It seems that most (perhaps all) EU members have free emergency care for everybody. If you go to a hospital (or worse get taken there by an ambulance) they’ll take care of you, no questions asked. So “go to the hospital, or wait till you get home” may seem like a reasonable strategy.
On the other hand side standard requirement for a Schengen visa is to have medical insurance. While US citizens do not have to obtain visas, they are still expected to comply with all the regulations, even though this rule is hardly ever being enforced. Pretty much the same goes with other (non Schengen) EU members.
It is not hard to find out if your policy works abroad. If it does not, travel medical insurance is not too expensive either.

so what is a good company to buy insurance from, i’ve seen so many adds online and I dont want to get scammed

@ Edyelchapin, it depends what coverage you already have. If you are a Spanish citizen then check to get the EU travel card insurance supplement.

For students, the ISIC used to include reimburseable insurance up to ~ $5K if I recall. Check it out as YMMV.

For North Americans, check out InsureMyTrip.com. It shops many providers, based on details you input, and shows you the policies that best match your needs at the lowest prices. I’ve bought short-term travel insurance from them, but never had to make a claim.

If you’re a student, check if your student insurance (often offered by the student union and is automatically added onto your tuition) includes travel insurance.