What do you mean? If a top website like wikipedia is allowing us to submit our link, you think this is spam?
social bookmarking is great solution. i have about 120+ links to social bookmarking services somewhere in my archive (cannot find it right now) but here is just little stratpoint for your internet research: hXXp://bloggerwhale.blogspot.com/2007/02/how-to-submit-links-to-60-social.html regards...
no need to register. it is free. for example: http://en.wikipedia.org/wiki/Advertising find the part: "External links" there is en "edit" part on right.click it. you will see external links codes. add your site at the bottom of the links. if the page's editor like your site, he will let your link to be online. you can find many wikipedia pages like that.for example, if your site is about maria sharapova, you can add to the pages: "tennis", "maria sharapova", "wta", etc.of course in different languages there are a lot of pages. one of my sites gets 80-90 visiters/day from one link in that kind of wikipedia pages.
also, you should be webmaster forums member.for example, v7n.com, forums.ukwebmasters.com, etc.each post means, you will get a visiter. for example, you see my signature(Add Your Link Free). normally, it has 3-4 new link additions/day. but when i use that signature in DP, it has 15-20 additions/day.i am a member of 7-8 forums.it is really very usefull for webmaster sites. signature,PR4 is working, maybe it had a hosting problem for seconds.seologs have problems in these days but my site is PR4.you can check it with google toolbar.thanks.
Yeah , The most valuable traffic is search engine traffic, So focus on your site SEO What is SEO? Just looking here then you can find some things about it.
I get most of my traffic from posting through myspace. I use my 26k 20k and 36k accounts and im generally happy with that method.
You may also do the following to get content to your forums. Use the forum as your blog and start threads frequently. This results in getting fresh content and increases the PR. Then you may get some hits from SE's and some new forum members. Hope that helped.
If you want to get lots of traffic through digg, do what others do and write something that's complete rubbish like: "Bush found with drugs!" You'll get 100 hits a minute! Although that's probably against their rules, so....be careful?! :S