The best manual social bookmarking service is Bookmarking Beast http://www.bookmarkingbeast.com . As you know it’s time consuming to register and post to all the top 25 or so social websites. With their service we are able to get quality one way social backlinks without doing any work ourselves. Not only do they submit to the most obvious sites such as reddit, twitter, stumbleupon, pinterest and others, but they also post to a growing list of hundreds and thousands of sites which has doubled our search engine rankings in the last 6 months.