Chess tempo has an endgame training mode that does exactly that.
Endgame Software

The best one is chessimo.Grows slowly in difficult but takes time and some money.I payed $ 10,00 in this, as an Ipad App

ChessTempo is useful, but I find they do not do much king and pawns only endings. Lots of rook + pawn vs rook drills. I am the cheapest guy I know, but blow $20 per year for 20 endgames/day.
Although limited to only 6 pieces, the table base
http://www.k4it.de/index.php?topic=egtb&lang=en
is useful.
And I had a queen vs rook interactive drill site in my favorites, but seem to have lost it. If interested, I can try to re-locate it.
Hello,
I'm looking for something like chess tempo or tactics trainer that focuses only on endgame positions. Do you know of such a thing? Also, looking for something free.