Extrema, originally developed in the fields of nuclear and particle physics, is a powerful visualization and data analysis tool that enables researchers to quickly distill their large, complex data sets into meaningful information. Its flexibility, sophistication, and power allow you to easily develop your own commands and create highly customized graphs.
StarPlot is a GTK-based program, written in C++, which can be used interactively to view three-dimensional perspective charts of stars. Charts can be recentered, rotated, or zoomed in or out with a mouse click (this can also, of course, be done via dialog boxes for more precision). Stars may be viewed (or ignored) by spectral class and absolute magnitude. Other features include support for both celestial and galactic coordinate systems, the ability to display extended non-stellar objects, and a pop-up Hertzsprung-Russell diagram. StarPlot is also packaged with starconvert, a utility which converts line-oriented stellar data records to StarPlot format. Most star data files available on the Internet can be converted this way if a short file describing the original file format is provided to starconvert.
ESO-MIDAS (European Southern Observatory Munich Image Data Analysis System) provides general tools for image processing and data reduction with an emphasis on astronomical applications, including imaging and special reduction packages for ESO instrumentation at La Silla and the VLT at Paranal. It also contains an applications packages for stellar and surface photometry, image sharpening and decomposition, statistics, and more.
SAOimage is a utility for displaying astronomical images under X11. Image files can be read directly, passed through a named pipe under Unix, or from a VMS mailbox from IRAF display tasks. It provides options for zooming, panning, scaling, coloring, pixel readback, display blinking, and region specification.
EQUINOX-3D is a 3D modeler with a very fast, fully integrated ray-tracer. It features read/write support for COLLADA, read support for Radiance's .hdr image format, 3DS (3D-studio) file format read support, multi-texturing, custom-programmable texture mapping, bump-mapping with automatic texture-space tangents, the ability to zoom into a region with "fly-to", and more. It includes a full runtime-class framework and a core design that allows for the addition of anything from a physics engine to a fully integrated renderer from a plugin. It is faster and more memory efficient than many other modelers.
Planets is a fun, interactive program for many-body gravity simulations. The emphasis is on play: it's easy to add in planets, zoom in and out, change the physical constants, save and load configurations, etc. It's designed to be easy enough for a kid to enjoy, but that hardly precludes adults.