Hey, I'm planing to start playing some chess, just to hold up some small skills.
Do you know any good chess clients?
I've looked at GlChess, PyChess and Knights, but I'm not sure which one is the best.

are you looking for a frontend or a backend ("engine") ? As frontend I use jose (http://jose-chess.sourceforge.net/). It comes with the toga-engine, which is a modified fruit I think, but can use all others I have tried as well. It's also good for analysing chess problems.
If you're looking for a backend, there are tons of free engines out there like crafty, zappa, comet, spike, hoichess, gnuchess, to name only a few. I play mostly against hoichess, because I can beat it from time to time. Engines like crafty, zappa or fruit way too strong for me.
Knights is cool to let 2 engines play against each other, but has trouble with uci engines.

Well, I am looking for a client. Not an engine.
Jose 3d mode seams nice. However rest of the program is a little ugly.
Perhaps because I'm used to gtk programs.

Dreamchess is my favorite. Depending on your distro it may or may not be in the repos. It is in Debian's.

I download some chess game and can not get them to play maybe I do ot know how to open them it keeps ask what program to open them in why