Please feel free to contribute, but send me a PM instead of posting here.
All these are based on shipping coin from that country to the United States and vice versa.
Australia
Delivery Time
The delivery time is rather long, sometimes up to two weeks, but it is not terrible.
Reliability
The Australian postal service is very reliable.
Regulations
Australia permits sending coins.
Canada
Delivery Time
One word: fast!
Reliability
Very good. Note: Numista has had a lot of Canadian swindlers. Though I don't think this is accurate anywhere else, please beware of returning veteran swindlers.
Regulations
Canada permits sending coins.
Netherlands
Delivery Time
Usually less than two weeks.
Reliability
The Dutch postal service is quite reliable, but it is not top-of-the-line.
Three payments to Romania "lost" claims to have never arrived
I'll trust the Swiss with a fortune
The French 90% of the time
UK better than the States
Netherlands is still up in the air; package still unaccounted for after two weeks.
remember i for i coins
swap list under reconstruction!
Italy, Poland - My multiple experiences sending to both were a crapshoot. This was over a period of 8 years for Italy and 20+ years for Poland. More items got through than didn't, but, the parcel and letter disappearances never stopped.
UK, France, Belgium, Netherlands - Service is pretty good, both to and from swaps as well as purchases from those countries have always arrived. Involved in more than a handful from each.
USA, Canada - Neither have ever presented me with a problem. I've been sending all over these two countries for as long as I can remember, we're talking regular, inexpensive, no tracking, no signature, lick a stamp or two mail service.
Cash in the mail is never a good idea anywhere. Sent cash from Sweden to the USA, also never arrived...
Sweden then: I would say the Swedish postal service is usually very fast. One working day to anywhere in the country, except the most northern parts (two working days). Letters are sent to where they should be sent, when they should be sent.
Sorting of letters is fully automated.
The post says they do not allow money to be sent through the mail, but as nobody checks I've had no problems so far. Personally I consider coins to be collectibles, not money. Money is something one can buy things with - which would mean only coins in circulation somewhere. Right?
Postage is quite high compared to most other countries. €15 for a letter 100 - 249 g, destination inside Europe.
In order not to break those automated sorters, no metal objects of any kind should be sent through the mail in letter post. When they mean paper money, it is for your protection and theirs, in case it gets lost/stolen.