Keith Devens .com

I would say: keithdevens.com/weblog/categories/5

This is because at this level: keithdevens.com/weblog/categories/ you are in the "categories" folder, with all categories optional for you to choose.

Neither I'd prefer /weblog/categories/name, where name is some kind of dirified version of the category name.

/category/5 ...seems to dound better

/category/5 - the other sounds like I've got 5 more levels to dive through

singular, definitely

I think of it like a classification... "5" belongs to the group "category" aka "5" is a "category". just like each "category" is part of your "weblog". So when I see that URL, I think to myself "This page is going to display all of Keith's weblog information that belongs to category 5"

However, if you use the plural form above, I would think to myself "This page is going to list category information for section 5" because a plurally named directory would imply (to me) relation to the structure of the system, while singular would imply content.

That's the way I feel on the matter, anyway.