Bitstamp, based in Slovenia
To be precise, Bitstamp as a company is registered in United Kingdom, but indeed the operation base is in Slovenia, and owner + staff are from there. It also uses a Slovenian bank for accounting.
I like the name bitstamp, because of some unknown reason to me (even for myself/conscious mind)
but it's reminds me "time stamp" ...
and I am/was bit involved with NTP sync servers ...