Which Sites Give the Best Back Links?
Back links can be made from any site really, they are simply a link from one site back to the original. The best back links come from sites relevant to the original site, from relevant link text, from a site with a good page rank, and only a small amount of other links coming from that page.
There are many different ways to make a good back link. You can write articles on many different article writing sites such as this one, (Factoidz), or you can make links from social bookmarking sites such as Digg, Delicious, Reddit, Mixx, RedGage, etc.
You should try to make sure that the site you are linking from has do follow links, because otherwise there will be no link weight flowing to the original site. You can get a free SEO toolbar download from SEO Book. This has a button which identifies no follow links.
Sites like Twitter and Facebook have no follow links, but Google has a separate algorithm which gives credibility to these links, if there are a lot of them from different accounts.
Stumble Upon has no follow links too, but if many people like your stuff, those sites are featured more often in their auto surf mechanism, which gives extra traffic to your site.
The traffic that back links generate can vary, but if you choose a site like Digg, Twitter or Stumble Upon, and work with a team of people, liking each other's sites, then that will work quite well to get a lot of extra traffic.
If anyone wants to swap a tweet, digg, or stumble, I will always return the favor when I can. Back links like these have little real benefit when only used by one person, but they are very useful when used by many.
The purpose of these sites is to identify the really popular sites out there, and show it to the other users, so that they might like it themselves, (or digg it), and so the cream rises to the top.
Some less popular social bookmarking sites are still valuable for creating do follow links, which boosts your Google rating, but the effect is mild at best. It could mean the difference between the second page of a Google search, and the first, which isn't bad really.
I spent a lot of time making back links to my articles on Associated Content, and then Bukisa, and for one reason or another, things changed within the site, and it made most of that work pointless.
I would suggest that article writers concentrate on writing articles, rather than making too many back links, because Google also has an algorithm for how often a site is updated with new content.
If you do want to make lots of back links easily, I suggest downloading the free browser add-on Add This. It has all the big names, and about a hundred other sites you can make back links from, but do it gradually over time, because Google likes to see a gradual build-up of the back links from different sites over time.