MetaPost is a powerful graphics language based on Knuth's METAFONT, but with PostScript output and facilities for including typeset text. Details on the language itself are available in various publications. See also http://www.tug.org/metapost.html and http://www.tug.org/interest.html The language and its implementation are now in the public domain.
MetaPost features curved arrowheads.
There is no "official" version of the MetaPost logo. Both versions are acceptable to me. I generally use "MetaPost" in places such as this web page where using TeX's logo10 font would be awkward. If you are using LaTeX's mflogo package, you might as well use \MP to get "".
MetaPost programs can output standard encapsulated PostScript files, but these can be difficult to deal with because of the use of TeX fonts such as cmr10. Such fonts are usually not resident on PostScript printers, so they have to be downloaded by a dvi-to-PostScript program that processes TeX output. Special care is required to ensure that fonts used by the MetaPost output get downloaded properly. One dvi-to-PostScript driver that supports this is Rokicki's dvips.