Social Bookmarking Service Required

Hello I am looking for a good social bookmarking service to promote one of my websites. The website has just over 100 pages. I would initially like to have 40 of these pages bookmarked on a number of different social bookmarking sites over a suitable period of time - I want it to look as natural as possible. Please pm the best bookmarking services you can provide, including the number of sites you will bookmark the 40 pages on and over what period of time you would recommend. I am looking for a long term provider that can work on all of my websites, so am looking for a good price. Many Thanks