flutterbird42,
ive been mailing packages home from just about every country i have visited.
what i can tell you is that most of them will have their own version of the US Post Office. Also, some of them will have their version of the "Priority Mail" boxes that maybe free and maybe not.
you can try googling for each countries postal service and see what rates they offer. you may have to dig for it or use the translated google pages, but it will give you an idea on rates.
what i have found so far is that there is usually a price break for packages < 2kg. Once you go beyond that, it gets more expensive. I will go out on a limb here and say to expect to pay about 60+ USD for a package around 2 kg (4 lbs) and this is from my experience so far. A disclaimer is that i havent been to half of the places you listed. Germany will be about 20~30 USD for 2kg (4 lbs). Paris, you can go to LaPost and check out their rates but you will have to dig for it. Amsterdam, i havent sent anything from there since that was usually my last stop and i just lugged it home. One thing though is that they dont have a post office anymore. you have to go to a convenience store for shipping.
i looked at the standard global shipping companies and i found that the rates were high(er) than i wanted. also, finding an outlet wasnt easy either. Germany has DHL all around the place and i feel its like their "post office" in general.
what you may want to do is to go to each country post office web site and look/jot down rates for the first 3 or 4 kgs of weight and cost. that way you will know what you into and if one country is really expensive, then hold off sending it until the next one. also, look at buying one of those travel scales. i bought one and made a long strap to go around boxes so i can have an idea on weight and cost before i go there. the scales dont take up much room and are handy in my opinion.
one handy rule of thumb (ROT) is that 1 kg = 2.2 lbs
happy trails.
edit to add.
what i also do is to bring a roll of shipping tape. it doesnt take that much space and you can use it and leave the rest when youre done. what i also found out is that not all boxes are made the same. there was a country i visited last year and the cardboard reminded me of the Chinese cardboard boxes that feel light as a feather and disintegrate when subjected to moisture. so, i always wrap the snot out of those boxes and also wrap the "To" address label so it wont get torn/worn off.
i also bring self addressed shipping labels with me with the "USA" added below the zip code. its saves time for me and also all handlers can read the nice legible printing.