Asymptote is a powerful descriptive vector graphics language for technical drawing, inspired by MetaPost but with an improved C++-like syntax. Asymptote provides for figures the same high-quality typesetting that LaTeX does for scientific text.
PyX is a Python package for the creation of EPS, PS, PDF and SVG files. It combines an abstraction of the PostScript drawing model with a TeX/LaTeX interface. Complex tasks like 2d and 3d plots in publication-ready quality are built out of these primitives.
PyTioga is for creating figures and plots with high quality text and graphics in PDF format. Text is processed directly by TeX (not an emulation), and the graphics covers a broad range of PDF features including images, curves, clipping, and transparency.