One thing that I have done sometimes is take positions from the book Endgame Challenge set up the position in Fritz and play the position against the computer. Don't really know of any sites that do endgame training other than chesstempo.
Where to practice end games?

Chess Tempo's Endgame training is still in Beta but it is excellent. There was a six man tablebase website but I haven't been able to find it lately. The nice thing about Chess Tempo is that you can set up personalized sets of puzzles based on material and then just practice practice practice. I don't think there's any other place that provides that.

Wormrose:There was a six man tablebase website but I haven't been able to find it lately.
Tablebase server linked at bottom.
I find tablebases invaluable when studying small endings... A lot of endgame studies have sidelines that you want to explore/understand better, and the tablebases make that possible.

One thing that I have done sometimes is take positions from the book Endgame Challenge set up the position in Fritz and play the position against the computer. Don't really know of any sites that do endgame training other than chesstempo.
This is how I have been practicing the endgame knowledge from part two of Silman's book. I read through the Silman chapter and then put like positions from Endgame Challenge and Pandolfini's Endgame book and played the position against the computer and AFTER that I would read throught the answers or solutions in the book.

Get Jeremy Silman's Endgame Course. Out of all of the endgame books... You will not go wrong with that one I promise you. Unlike most books, it is in sections by class and rating so you should know what a "B" or "C" class person should know at that level. I've been through ton's of different books and I liked that one the best. As far as endgame training online, it's okay but its one of those things that I think sticks with you better if you do it over the board (as opposed to openings)
I know this site http://chesstempo.com/chess-endgames.html
You know any other good place?