SEO Analyser

If you've been using SEO analysis tools and are having trouble deciphering what they're telling you, try SEOAnalyser.net. This tool provides actual explanations for the metrics it provides you, allowing you to read what you can improve or see what's working.
http://www.seoanalyser.net

Email Marketing Calculator

Email Marketing is a key function to increasing your sales, as it's the most direct form of contact with a potential consumer. Like all forms of marketing, it's important to know what your ROI will be upon implementation, which you can find out with this Email Marketing ROI Calculator. 

http://www.bplans.com/business_calculators/email_marketing_roi_calculator

Analyze Your Website's SEO

If there's a particular keyword/phrase you're looking for your website to improve upon in terms of SEO, try this SEO Keyword/Phrase Analysis tool. It provides insight for all sorts of content elements, along with technical improvements. 

http://www.reactionengine.com/

Find Out When a Website Is Tracking You

Ghostery is a browser add-on available for Chrome, Firefox, IE, Opera, and Safari. With it, you can detect when your browsing is being tracked. It will then show you who's tracking you, along with information about the company. You can then choose to block the service or choose other options moving forward. 

http://www.ghostery.com/

Social Media Management Tool

SocialOomph is a neat web tool that provides a host of free and paid productivity enhancements for social media. You can do a lot with the site which includes functions for Facebook, Twitter, LinkedIn, Plurk and your blog. There are a ton of useful Twitter features like scheduling tweets, tracking keyword, viewing mentions and retweets, DM inbox cleanup, auto-follow and auto-DM features for new followers. Social Oomph will auto-follow any new follower of yours on Twitter if you like, which could save you a ton of time if you normally like to reciprocate follows. Social Oomph is so effective at increasing social media productivity.

https://www.socialoomph.com/