The most comprehensive single volume about the mathematical theory of tiling is Tilings and Patterns, by Branko Gruenbaum and G.C. Shephard. (See Amazon.co.uk or Amazon.com.) I try to use the notation and terminology used in this book. There is a whole chapter on aperiodic tilings, and one on Wang tilings, as well as a feast of diagrams. Highly recommended.
A popular and compelling introduction to Penrose tilings can be found in the first two chapters of Penrose Tiles to Trapdoor Ciphers... and the Return of Dr. Matrix, by Martin Gardner. (See Amazon.co.uk or Amazon.com.)
The classic text on polyominoes by their inventor is Polyominoes: Puzzles, Patterns, Problems and Packings, by Solomon W. Golomb. (See Amazon.co.uk or Amazon.com.)
A real mine of information and miscellanea on tiling, and geometry in general, is The Geometry Junkyard. Particularly interesting, from the point of view of this project, are the sections on tiling, Penrose Tiles, and polyominoes.
Chaim Goodman-Strauss has devised A Small Aperiodic Set of Tiles. His distinctive pair of tiles, the trilobite and cross, have been incorporated into the Alhambra program, so you can produce tilings with them.
The search for pentagons that tile the plane monohedrally is a problem with an interesting background (see Gruenbaum and Shephard for details). Bob Jenkins has found some new pentagons, and Mike Korn uses such tilings as background images. Ed Pegg Jr has written a summary of all known classes of pentagons that tile the plane monohedrally.
Finally, for a good site that's nicely designed and contains lots of (not too technical) information, try out Totally Tessellated.
Computer Graphics for Java Programmers, by Leen Ammeraal. (See Amazon.co.uk or Amazon.com.)
Doris Schattschneider has compiled a long list of tiling software for a variety of platforms. Two that stand out are a Java Penrose Tiler, and Java Kali, which allows interactive drawing of wallpaper, frieze, and rosetta groups.