Books
Learn Chess Tactics by John Nunn
One of my favorite tactics books. Each chapter teaches a specific tactic and then presents increasingly difficult puzzles to help you learn the theme. A great combination of learning and practicing.
Chess: 5334 Problems, Combinations, and Games by Lazslo Pulgar
A very big book of chess problems both in length and girth. This book focuses on checkmates, and is very good practice for developing your chess vision.
How to Beat Your Dad at Chess by Murray Chandler
Chess Tactics for Kids by Murray Chandler
These two books are aimed at young kids, but they are nevertheless valuable lessons at any age. Every two pages are a new lesson, so it's easy to study in small chunks.
Practical Chess Exercises by Ray Cheng
A challenging book for advanced students. This book mixes tactical and positional exercises at random so that you are forced to study each problem to figure out its theme. A great way to practice evaluating positions.
Online
For those who would like to work on tactics online, there are two resources that I like. For thoughtful study, I really like the Shredder Chess weekly chess problems. The problems go from level 1-8 each day, so it starts easy, but the challenge increases. Try to see the whole solution before you make the first move, but don't worry if you can't find it. If you don't see the answer to a problem within a few minutes, go ahead and look at the answer, then go back and study the original position and calculate the answer in your head. This is great practice for calculating over the board.
For tactical vision, I like the Chess Tactics Server. You can play as a guest, or you can create your own sign-on. This site challenges you to solve the problems as quickly as possible, but again don't worry too much about the rating. You can do a lot of problems in a short amount of time, which is a great way to hone your tactical vision. Useful when you have a superior position under time pressure in a real game.
