OpenRefine (http://openrefine.org) - a powerful tool for working with messy data: cleaning it; transforming it from one format into another; and extending it with web services and external data.
Breve (http://hdlab.stanford.edu/breve/) - gives you that meta view of tabular data and also lets you drill down to records and columns, and edit values. Nice colorful views of your data.
DataBasic (https://databasic.io/en/) - a suite of easy-to-use web tools for beginners that introduce concepts of working with data. Includes basic text analysis, csv explorer, file diff, network graph of connected data.
Atlas.ti
Recogito
RAW Graphs (https://rawgraphs.io) - open source data visualization framework built with the goal of making the visual representation of complex data easy for everyone. Takes data from a spreadsheet and turns it into a beautiful graph :)
Data Viz Project (http://datavizproject.com) - a searchable, visual inventory of data visualization types with descriptions and real-world examples. It's awesome.
Tableau
Palladio
Mallet