It is a popular fact that and major search engines like Google, MSN and Yahoo give more weightage to content in a website. Therefore it is likely that the more places you have for your content the greater traffic you are can generate. Hence submitting your site manually into social bookmarking sites like blogthis , Digg, orkut and others will not just generate a greater volume of direct traffic but will also help increase the SERP (Search Engine Results Page) of your website.