Product: uDig
Download Website: http://udig.refractions.net/download/
License: LGPL license
Operating System: Windows, MacOS, Linux

uDig is the "User-friendly Desktop Internet GIS." Although it was not the first open source GIS product created, when I first used it in 2007, I knew it was for me. uDig hits a rather powerful punch, including support for local data, databases and Internet data. From the start (way back in 2004), it was designed as a general purpose development platform. And it continues that tradition today. 

uDig is a nice spatial data viewer and editor, with special emphasis on the OpenGIS standards for Internet GIS, the Web Map Server (WMS) Service and Web Feature Server (WFS) Service standards. It provides a common Java platform for building spatial applications with open source components.

Perhaps one of the more appealing features of uDig is its user friendly interface (I would describe it as a beefed up Google Earth interface). In addition, uDig is easily installed and comes with a set of "walkthrough" tutorials, which help to make the user experience quite pleasant. uDig has a large community of users and followers, with easily accessible "tips" and online help readily available on the uDig “users” web page -- another big plus.

Some of the other useful uDig features are:

• Drag and drop support across all platforms. With this feature, users can drag GIS files and Web service URLs directly into the application. Once dropped into the application, the files are then automatically loaded into the map view.
• Geographic information can be obtained in a variety of formats and coordinate projections. Through the use of on-the-fly projection, information is seamlessly displayed on the same screen with no manual intervention.
• Another powerful tool is uDig's use of public catalogs to locate free spatial information using a "search and see" workflow.
• Support for a wide range of GIS formats and services, including Shape, ArcSDE, OracleSpatial, PostGIS, DB2, OpenGIS WMS and OpenGIS WFS
• uDig utilizes a unique streaming architecture that allows visualization of large quantities of data (Teradata support). This enables uDig to operate on a reduced hardware footprint (making it an attractive target for in-the-field and relief work).

The uDig website offers a gallery of example applications that show how uDig is being used. In my class, students review these case studies as illustrations of how GIS is used to analyze and solve spatial problems.

Examples include the following:

1. The DEWS Project (tsunami Distant Early Warning System, funded under the 6th Framework Programme of the European Union)
2. The BC Ministry of Forests has created a tool in uDig to merge multiple road network layers into a single consistent, connected network.
3. In Peru, the International Potato Centre (CIP) has used uDig as the framework for its latest release of DIVA GIS, an analytical tool for potato genetics.
4. Using uDig, Eurobios has built a routing and logistics package for municipal trash collection programs.
5. JGrass is a free, open source GIS based on the uDig framework. JGRASS uses the algorithms of GRASS and the user-interface of uDig to provide hydrological and geomorphological analyses.
6. Arbonaut (a Finnish technology company) is using uDig as a framework to build ArboGIS and Taaka, proprietary forest land management applications.
7. In the United States, the Army Corps of Engineers is building AutoCad format support into uDig to support its applications.

I have used uDig in my introductory geospatial technology course as a stand-alone GIS desktop application to introduce fundamental GIS concepts such as query and analysis. From an educator's perspective, uDig is an absolutely wonderful tool. It is multi-platform (including Windows, Mac and Linux) which allows just about any student with a computer to download it. The two "walkthrough" tutorials and demonstration videos available on the uDig website are easily understood and very user friendly. Students in my class complete the first two out-of-the-box tutorials as well as an additional set of four tutorials that I created. Students acquire Internet-available data and then use uDig to perform basic GIS tasks. Course surveys indicate that students enjoy using uDig. They consistently report that uDig helps them learn fundamental GIS concepts. And -- perhaps most importantly -- they find it easy to install and use.

For the professional, uDig offers the ability to create and add new functionality using the Eclipse rich client platform (RCP), an industry-standard extension framework.  With Eclipse RCP, users can create feature-rich, stand-alone application plug-ins.  uDig also includes a substantial toolkit of Java functionality, upon which developers can build. The out-of-the-box feature set is easy to use with a native set of relatively powerful tools. Ultimately, uDig can be used as a stand-alone application, it can be extended with RCP plug-ins, and it can be used as a plug-in in an existing RCP application.

Free, user friendly, open source; it doesn't get much better.