Google My Maps allows you to put custom markers (including text, images and videos) on a google map.
Carto is a powerful web based GIS tool with a robust free option.
Node XL is template for Excel. Available in both a paid and free version. It allows you to pull data from Twitter, Facebook, YouTube, emails, and more and visualize the resulting network.
Palladio is a web-based tool designed with Humanists in mind. It allows you to visualize and map data imported via .csv file.
Google Fusion Tables are a web-based GIS tool that let you easily map a large number of points.
Voyant is an easy-to-use, web-based tool for text mining and text analysis. There is nothing to download and it works with a wide variety of file types.