Mention (#20)
Mention is the “be in the know” tool for marketers to understand what social media influencers are saying about keywords or topics. Mention also has comparative analysis and sophisticated change-over-time graphs for trend analysis.
SEMRush (formerly QuickSprout) (#19)
SEMRush (aka QuickSprout) gives you an intelligent view into keywords, gap analysis, marketing insights, topic research, and more.
SpyFu (#18)
SpyFu is a tool to let you look at paid keywords across Google AdWords and understand the market (supply & demand) for the keywords you are buying. It can also be used for organic search analysis too.