Past stands for Palaeontological statistics. It is a free to use data analysis tool for paleontology, ecology and other related fields. It has spreadsheet type data entry form interface.
It supports graph, scatter, 3D scatter, bubble, histogram, kernel density estimation, box, percentile, ternary, survivorship, spindle, matrix, surface and normal probability plots. You can open .dat, .nex and .nts format files using this program. It has lot of options to plot and analyse data quickly without too much effort.