The DZone Essential PostGIS reference card got released yesterday. The PDF version is a free download, though does require DZone registration. This reference card is focused on PostGIS 2.1 but does showcase some features present in older versions. Its way too hard to stuff everything on a 9 page reference so we had to leave out some of our favorites that we thought would not be as appreciated by a developer community just starting off with GIS and PostGIS.
We are working on the second edition of Essential PostgreSQL which hopefully will be out in the next 2 months. That one will be advertising our upcoming second edition of PostgreSQL: Up and Running..
On a slightly related topic, we did our Intro to PostGIS talk. We had a good live demo with very few glitches followed by food and spirits. The group of folks was a good cross sectional. Web developers working with geodjango or ruby on rails new to PostgreSQL and PostGIS, some mainstream GIS (urban planing) with little familiarity with relational database spatial (but familiar with ESRI), retired professor, high-end PostgreSQL folks with limited knowledge of PostGIS, IT consultants both GIS and mainstream etc. We promise to have the code posted probably early next week (and possibly a video too if the video turns out okay).