There are a lot of link building, publicity and social media tools out there to help you build links and market your site. Here are the tools I know about, have used or my friends use and like. Some of these links are affiliate, most are not.
SEOBook Public Tools (free)
SEOBook SEO Tools (membership Join Now)
SoloSEO Link Tool (free) Search on your keywords plus a metric and it brings back sites you can add your link to “your keyword + directory”
Open Site Explorer (free and membership) Backlink checker and analyzer
Bad Neighborbood Link Checker (free) Tool will tell you if the site you want to link to is associated with “bad” sites through linking
Majestic SEO (free and paid) Backlink checker and analyzer
Link Research Tools (paid) Has multiple link building tools, good one.
Ontolo Tool Set (free and paid) Prospecting and analyzing tool. Good one but not for newbies.
Ice Rockets (free but loads slowly) Tracks trends, reports what’s hot
Google Trends (free)
Trend Watching (free and paid) Sign up for the trend report and keep up with what’s trending
Broken Link Checker (free) Checks for broken links
Xenu (free) Old time favorite
Langreiter Tool (free) I’ve been using this one for years, love it. Search on your keyword and it will compare search results between Google and Yahoo!
HighRankings (free) Jill’s longtime SEO newsletter
Link Moses Private (membership) Eric Wards private newsletter