ConocoPhilips developed CPSeis, and released it as open-source package.
It offer some useful features, that you would find in commercial packages, such as:
A velocity picker
A cube viewer
Running jobs on other machines
residual NMO trim
generate synthetic traces
attributes (e.g. instantaneous frequency)
trace header math
Here I show some examples of what you can do with it.
Some public datasets have been processed with CPSeis, and are available here.
Reports are .odt files, and require OpenOffice, LibreOffice or Word 2007 SP2.
SEG Y files are mostly 16-bit integer format. Images are PNG format up to 1920x1200 pixels. Images are not the whole line, but typically one-third of it, scaled for reasonable trace density.
Also some sample workfiles (as tar archives) are available, so that if you download one of these datasets, you can load the workfiles into cfe and begin trying CPSeis.