Wow, according to comments and email, there are many more "folders" fans than I would have guessed! So, I spent a little time going through the lists I created, and looking at some new sites, to see if there was anything out there that wasn't simply a re-hash of something else already out there (which is how it goes in 2.0 land).
So, for you folders folks, I highly recommend Netvouz. Netvouz lets you create folders, people! It also tags, has a decent social set-up, and clean interface that is similar but a touch nicer to look at than delicious (if you care). You can import your bookmarks from any service that lets you export them to a file, which is nice. One word of caution: if you are exporting from a service that does NOT have folders, you will either have to create and move links into folders after you import them (a pain if you have a lot of links), OR you can create the folders first, them import your links in groups (easier in my opinion). In any event, you'll have to noodle around with the service a bit to get the hang of creating folders and such, but if its folders you want, folders it's got. Runner-up: Backflip. Yep, Backflip is still around. Kinda old school in the looks department, makes you jump through a few hoops at sign-up, does NOT support tagging (really), and the social aspect is clunky at best - but if you just want to store your "favorites" in folders, on the web, you might want to check it out.
I checked out a couple of other bookmarking apps, but didn't see anything too new or exciting - though I will add Raw Sugar to the list on the Social Software page, because I forgot to include it the first time around, and it is a pretty popular tool. Yahoo has jumped on the bandwagon with its MyWeb - nothing new here (yet - it's still in BETA), but a good addition for those who use Yahoo as their online base of operations.
I also checked out Tumblr after reading Kaijsa's comment. Tumblr is actually closer to Linkwalla than it is to the other social links sites, as it creates a links "blog" rather than just a list. Tumblr's floral icon is reminiscent of Magnolia (hmmmm), and it's easy to use. Probably not for everyone, but like Linkwalla, I think the concept is interesting.
Lastly, Linkwalla's creator, Ben Brophy, turned me on to a nifty little tool that allows you to post to several services with a single click - nice. I'm not sure that the service is actively supported at this point, but if your bookmark sites are on the list, it's a great tool to have in the box.