Does Google provide a http page to return a XML route?

I have been using a lot of Google Maps's API for getting geocoding and reverse geocoding services.

Do you know if there's a service (through http) that would return a route?

Yes, you have to use DirectionService from the Maps API.

... and if you are using the Version 2 API, you can use GDirection class.

I thought I should clarify that both the v3 DirectionService and v2 GDirection classes are part of the JavaScript Google Maps API.

If you are looking to access the Google Maps API Geocoding Service directly over HTTP then as far as I know you are limited to Geocoding and Reverse Geocoding requests.

It is quite possible that this service does exist and I have missed it (please let me know if this is the case).