Pathauto has a feature to remove less important words from rewritten URLs in order to save space without compromising semantical meaning, or potentially, usefulness in search engine optimization (SEO).
This page gives suggestions on strings could be used for removal on the administration page in various languages. Please add more. A good starting point seems to be most words that are prepositions. You could also advertise this page in you national Drupal group (groups.drupal.org).
For reference, this is the default list included with the module (English):
a, an, as, at, before, but, by, for, from, is, in, into, like, of, off, on, onto, per, since, than, the, this, that, to, up, via, with
Note: Languages should be placed in alphabetical order, so it is easier to locate them. Words within the lists should also be in alphabetical order.
Dutch
aan, als, bij, dan, dat, de, deze, die, dit, door, een, er, het, in, is, maar, met, n, naar, om, op, per, sinds, uit, van, via, voor, zoals
French