The association of investment trusts in the UK have a very good site where you will find listings, literature and more. Not true that they are a UK animal (though very popular there), the USA has multiple investment trusts (called closed end funds) and there are others in Europe (diversified holding companies and the like). You are right in that they are not organised as well outside the UK however (exception of possibly the USA).
As to why not as popular, a large amount of it has to do with commissions (in that they don't offer them to financial advisers => they don't recommend them). That being said they are actually quite popular.