Flock is a new flavour of Mozilla browser (www.flock.com) it has some nice features, like a "write blog" option that lets you type up a piece like this one and post it straight from the browsers own page.
Also has a built in Flickr browser and "upload" drop zone (though it doesnt work yet - much like the "blog it" drop zone), and features the ability to sync your bookmarks (after it smartly imports all your history and favs from Internet Explorer on first run) with online services like del.icio.us (http://del.icio.us).
I had to delete my del.icio.us account 3 times trying to get "just" my bookmarks uploaded and not history and other rubbish - there isnt a setting that controls this it seems.
And more often then not the browser tends to fall over and not do anything, or in my case break completely (had to reinput my blogger details into it).
This browser is only at beta stage but is nearing completion, so I would wait awhile to pick this up - but it is alot of fun - and has a built in RSS aggregator (scans all your bookmarks for RSS leads and collects all the news into one webpage!).
I would give this a 3 out of 5, and del.icio.us will get a 3 also - as it seems adding tags are useless unless you have a nice search option somewhere, and also a batch editing and tagging options (as well as a delete one would be nice)!.