It is often stated that for players rated <1800 that Chess Tactics should be the main focus of study for improvement.
"Tactics are the heart of the game"
If you are not already using the TT on Chess.com then Chess Tempo is the best alternative.
http://chesstempo.com/
Described as an online chess tactics training site that includes a database of 2 million games, endgame training, and the ability to create custom problem sets.
It is often stated that for players rated <1800 that Chess Tactics should be the main focus of study for improvement.
"Tactics are the heart of the game"
If you are not already using the TT on Chess.com then Chess Tempo is the best alternative.
http://chesstempo.com/
Described as an online chess tactics training site that includes a database of 2 million games, endgame training, and the ability to create custom problem sets.