NEMO

NEMO was probably the first package developed by the MODEST lineage of people, back in 1986-1987 at IAS, Princeton, by Josh Barnes, Piet Hut and Peter Teuben, and now maintained by Peter. Apart from a number of N-body integrators (the original B&H 1986 treecode, Walter Dehnen's treecode etc.), you can find tools to work with orbits, images, tables, FITS files and the various conversions between them where they make sense.

More to come.