I sort alphabetically, purely because I think it might help someone who is checking the directory to see if their own site is listed.
PR is Google's measure of the importance of a page, and it's obviously flawed and entirely irrelevant to directory listings.
I do agree that there's some unfairness in the way sites are sorted. But this is only an issue if you have an unwieldy number of listings per category anyhow. More than 20 and it's time for a new subcategory anyhow. It might mean moving some sites further down the directory tree, but at least that way the listings are more specific to a certain topic, so a user is more likely to find what they are looking for.
-- This message may have been cut off and the rest will only be shown to members. To become a member, click here --