I just stumbled upon this useful article on Search Engine Friendly URLs which is filled with wonderful tips on choosing the right URLs for your website. It isn’t written specifically for blogs but the information is useful to keep in mind when setting up the way in which your blog comes up with URLs. It has a good section explain the pros and cons of ‘Dirty URLs’ or those URLs that tend to be filled with numbers and punctuation marks rather than words.
This article will be more helpful of course for blog users using systems like WordPress and MoveableTyle that allow you to customize the way in which your URLs work. Here’s a taster:
‘The first path to better URLs is to design them properly from the start. Try to make the site directories and file names short but meaningful. Obviously, /products is better than /p, but resist the urge to get too descriptive. Having www.xyz.com/productcatalog doesn’t add much meaning (if a user looks for a product catalog, they might well expect to find it at or near the top-level products page), but it does needlessly restrict what the page can reasonably contain in the future. It’s also harder to remember or guess at. Shoot for the shortest identifiers consistent with a general description of the page’s (or directory’s) contents or function.’
Read more at URL Rewriting – Search Engine Friendly URLs