A Semantic Web Reference Card
The UMBC Semantic Web Reference Card is a handy "cheat sheet" for semantic web developers and programmers. It can be printed double sided on one sheet of paper and tri-folded. The card lists common RDF/RDFS/OWL classes and properties, popular namespaces and terms, XML datatypes, reserved terms, grammars and examples for encodings, etc.
Really neat: this reference card
covers most of the stuff one needs when working with RDF "manually". [source: Planet RDF