There are many types of links that we deliver in every SEO campaign from $100 to $10,000 and most of them are put within these categories:
Article Links: Those links comes from published articles. As an example you have E-Zine Articles.
Blog Comment Links: Those types of links are obtained when you comment on a blog while referring to your own website. Not all websites allow comments and the majority of them who do append the rel=”nofollow” tag to all of their posts.
Directory Links: Those are the links that comes from directories. Remember, the best backlinks are those who are relevant. There are lots of high quality directories which you can submit your site to. The top ones are the yellow pages, Yahoo! Directory and the Open Directory Project.
Forum Comment Links: Similar to blog comments but they come from the comments placed in forums.
Guest Blogging Links: Those types of links are obtained when you write a post on another blog.
Indexer: These types of sites are often found in research website directories (PR3+ ONLY) where you can find & test various things about your site. Often an SEO link check, domain value assessment, up-check or other assortment of tools to test, pull and squeeze your website for compatibility. These sites are often skipped by Google, but add a nice softening to the link building and have a 0.05% chance of getting indexed!
PHP Exploit: A unique type of link that inserts your keyword as anchor text into the PHP version of a website. While this is not visible to the human eye on the website, it is perfectly visible by the spiders of Google/Bing/Yahoo when they sort through the website's code.
Press Release Links: The press release backlinks are still considered effective type of links even after the latest Google’s update. Press release sites are similar to article websites but they are directed for the news and media. A famous one is PR Newswire.
RSS Feeds: Those are knows as “Really Simple Syndication”, RSS feeds allow webmasters to share their content with those who subscribed to their channels and feeds.
Social Media: Also known as Social Signals - these include facebook likes, twitter retweets, google+, check-ins, addthis, tumbles, repins and more. It could also be your main twitter, facebook, youtube page that your company is located at (these are good PR9 back links).
Trackbacks: A type of link back methods for website authors to request notification when somebody links to one of their documents. This enables authors to keep track of who is linking to their articles.
Web 2.0 Links: Those are popular backlinks that comes from a wide range of websites that provides users a way to create their own pages, sites or community pages. Web 2.0 allows uses to share their information and websites. Popular examples include: Squidoo and Weebly.
WhoIs: These links are especially important to getting new content out there and indexed by Google. WhoIs are basically a similar form of Indexer backlinks.