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One of the most important areas of chess to improve is also one of the easiest. Chess tactical abilities can be trained simply by solving lots of tactical problems. One simple and good way is to have a pocketbook with problems, and solve them from the diagrams without using a chessboard.

I just found another, quite entertaining way:

http://chess.emrald.net/index.php

This is the "Chess Tactics Server", a free service created by a German chess club. Highly recommended, I will be using it a lot.

One more page for training your tactical skills: "CHESS TEMPO". It is better than Chess Tactics Server. More options. In adition, you have on Chess Tempo possibillty of training chess endings too.

Thank you both for the links. I've found them tactically stimulating so far.