PSQL is the command line administration/query tool for PostgreSQL. It is simple, light-weight and packed with a lot of charm. Unfortunately we can't quite capture all its charm in a single pager cheat sheet, but hopefully this will give you a sense of its usefulness.
Below is a Thumbnail view of the PSQL cheat sheet. This is by no means comprehensive, but are the features we use most often. It is also pretty much what you get from the help screen with just some added color.
PDF Portrait version 8.5 x 11" of this cheatsheet is available at PSQL8.3 Cheatsheet 8.5 x 11 and also available in PDF A4 format and HTML.
Hubert has some neat tips for making more effective use of psql