I'm something of a zealot about short, readable URLs. Most people by now are using server rewrite rules and Front Controllers of some sort to keep the paths in their application sane and legible, but an area that's often overlooked is the querystring, especially after a form submission.
A typical example of a situation with a 'messy' querystring might be a search form on site. When a form is submitted, all the elements in the form are entered into the querystring whether they're relevant or not.
That leads to querystrings like /search?size=&shape=&colour=red&age=, which would be a lot more legible as /search?colour=red
On some sites I work with, an 'advanced search form' can have up to 20 elements, all of which might get submitted in one go leaving the search results page with a huge URL.