Is there a Web Service available for 6-piece endgame tablebases? I use the LokaSoft web service for 5-piece endgames, but cannot find one for 6 pieces.

BTW, by web service I mean a software function capable of being called over the internet (see http://en.wikipedia.org/wiki/Web_service), not simply a service being offered on the web.
We can find several website giving 6-piece endgame tablebase, the tricky part is probably the way you want the information back.
Here is 2 examples of endgame tablebase :


http://www.shredderchess.com/online-chess/online-databases/endgame-database.html
http://chessok.com/?page_id=361


In both of this example you can ask a position by putting FEN code, so there is probably a way to use it as a webservice. (Perhaps you'll have to use a script)

Also another suggestion, on the link section of http://en.wikipedia.org/wiki/Endgame_tablebase you can find Nalimove database and try to make it communicate with your software.