In your humble opinion: what would be a best practice aproach to map REST URLs to services/files within one's architecture (let's assume MVC pattern here)?
In addition to Darrel's answer:
Make use of the hierarchical nature of HTTP URIs; think of every path segment as drilling down into the overall space of managed items (e.g. orders, customers). If at some point you need to 'index' into a collection along multiple dimensions (e.g. query) then use query string parameters:
/service/products/cars/japanese-cars/toyota/corola/&priceMin=2000&priceMax=5000
Note that (as darrel said) the structure should be opaque to the client. That means that the client needs to discover the parameters at run time (that is what forms or URI templates are for). Of course client and server need shared knowledge about the meaning of e.g. priceMin. That knowledge should be in some design time specification, for example the specification of a link relation. Maybe look at http://www.opensearch.org for detailed use case.
Also interesting is the host part of the URIs. If you might at some stage need to move parts of your services to another machine, design your URIs so that the relevant information is in the domain part. Then you can use simple DNS to route requests to different machines.
HTH, Jan