The basic idea behind open source is very simple: When programmers can read, redistribute, and modify the source code for a piece of software, it can be adapted and continuously improved. The open source movement has led to the development of numerous software tools that often match commercial products in quality and sophistication.

Below is a collection of free software tools that are of potential interest to anthropologists. All these tools are free and many of them are cross platform.

Picasa Photo Organizer (http://picasa.google.com/index.html)
Instantly find, edit and share all the pictures
PC only

Inkscape (http://www.inkscape.org/)
Vector Graphics Editor, similar to Adobe Illustrator
all platforms

Image Magick (http://www.imagemagick.org/script/index.php)
Software suite to create, edit and compose bitmap images. It can read, convert and write images in a large variety of formats
all platforms

GIMP Image Manipulation Software (http://www.gimp.org/)
Program for photo retouching, image composition and image authoring
all platforms

Blender 3D Software (http://blender.org/)
Software for 3D modeling, animation, rendering, post-production, interactive creation and playback
all platforms

Audacity (http://audacity.sourceforge.net/)
Free, fully-functional multi-track audio software for recording and editing sounds.
all platforms

Transana (http://www.transana.org/)
Software to analyze digital video or audio data. It supports transcription, assigning of keywords, complex collections of interrelated clips, exploration of relationships between applied keywords, and sharing.
PC only

WeftQDA (http://www.pressure.to/qda/)
Easy-to-use tool to assist in the analysis of textual data such as interview transcripts, written texts and fieldnotes. It includes a number of fairly standard CAQDAS features
PC and Linux
TAMS Analyzer (http://tamsys.sourceforge.net/osxtams/)
TAMS Analyzer is a program that works with a Text Analysis Markup System (TAMS) to let you assign ethnographic codes to passages of a text just by selecting the relevant text and double clicking the name of the code on a list. It then allows you to extract, analyze, and save coded information.
Mac
AnsWR (http://www.cdc.gov/hiv/software/answr.htm)
AnSWR (Analysis Software for Word-based Records) is a software system for coordinating and conducting large-scale, team-based analysis projects that integrate qualitative and quantitative techniques.
PC
Scribe http://chnm.gmu.edu/tools/scribe/
Note taking program that allows you to manage your research notes, quotes, thoughts, contacts, published and archival sources, digital images, outlines, timelines, and glossary entries. You can create, organize, index, search, link, and cross-reference your note and source cards. You can assemble, print, and export bibliographies, copy formatted references to clipboard, and import sources from online catalogs. You can store entire articles, add extended comments on each card in a separate field, and find and highlight a particular word within a note or article.
all platforms

CMap Concept Mapping Software Toolkit (http://cmap.ihmc.us/)
The IHMC Concept Mapping Software empowers users to construct, navigate, share, and criticize knowledge models represented as Concept Maps.
all platforms

Google Earth (http://earth.google.com/)
Offers maps and satellite images for complex or pinpointed regional searches.
Mac and PC

GRASS GIS (http://grass.itc.it/)
Geographic Information System (GIS) used for geospatial data management and analysis, image processing, graphics/maps production, spatial modeling, and visualization.
all platforms

ImageJ (http://rsb.info.nih.gov/ij/)
Software to display, edit, analyze, process, save and print 8-bit, 16-bit and 32-bit images. It can read many image formats including TIFF, GIF, JPEG, BMP, DICOM, FITS and "raw" and supports "stacks", a series of images that share a single window and is multithreaded. It can calculate area and pixel value statistics of user-defined selections. It can measure distances and angles. It can create density histograms and line profile plots. It supports standard image processing functions such as contrast manipulation, sharpening, smoothing, edge detection and median filtering and spatial calibration to provide real world dimensional measurements in units such as millimeters.
all platforms

Skype (http://www.skype.com/)
Peer to peer voice service. Users may call landlines and cellphones for a minimal fee; users may call each other for free. Free software, but not open source, as the source code is not available.
all platforms

R (http://www.r-project.org/)
Language and environment for statistical computing and graphics. R provides a wide variety of statistical (linear and nonlinear modelling, classical statistical tests, time-series analysis, classification, clustering, ...) and graphical techniques, and is highly extensible.
all platforms
GGobi
http://www.ggobi.org/
GGobi is visualization software for viewing high-dimensional data. A variety of multivariate graphics such as tours and parallel coordinate plots are available. Plots are interactive and multiple plots are linked with user brushing and identification. The methods have grown from exploratory data analysis, an area pioneered by John Tukey, building on the current fast graphically capable desktop computers to enable highly interactive, real-time, dynamic exploration of data.
all platforms