Flock is getting really usable right now. The version is titled 0.5+, and while I don’t know what the plus stands for, this version works well. The Bookmarks can be made private or public now, Flickr integration works well, it loads faster than 0.4, it is way more stable. All in all, Flock seems to be on the right path. They seem to have taken some Venture Capital on the way as well - seems to help.
By the way, try Protopage if you are using a modern browser (that excludes IE and Safari): A great example for AJAX use, and a great dashboard/blackboard if you want to leave some notes on a virtual fridge for your loved ones far away. I even got my girlfriend to use one with me - and she likes it! You can make your protopage public or private, even upload your own background and make it your home.