Good training sites/tips

Hello! I have trained my tactics on this page http://chess.emrald.net/index.php. However im starting so see the same tactics twice (which makes it extremly easy). So im wondering if you know any good sites for training tactics but also endgame and openings. Since im a poor student it would be great if it was free or at least very cheap. 

I feel like I got all the time in the world studying chess but I just don´t know how I should study, if anyone have any good ideas please share them. I find it very boring to analyse positions, I just don´t got the patient if it´s not a real game of mine and sometimes not even then. Is there any good way to improve your calculation speed/depth and analysis? I feel like ive lost tons of games because  i didnt calculate my move and just as many because i calculated a good move as bad (my intuition said it was good, then my calculation said it was bad). 

Many questions and very unstructured but if you have an answear to at least one of my questions please let me know :)

this site, tactics trainer

chesstempo is awesome

Check out Chess Tempo (.com I assume).  365chess.com also is of interest.

here's another tactics site:

http://www.ideachess.com