I am a new play, I bought cards a while back and am wondering what sets are legal in organized play. I have cards back from 2005 and I just want to know if they are still usable.

Thanks,

Summerz

You can check AGoTCards to see which sets are legal; anything listed after the Core set in the cards section is legal, though there is a growing restricted list which has resulted in some cards basically being "soft-banned." The Clash of Arms cycle is about to be reprinted so buying that is not recommended. Off the top of my head (I'm sure I'll forget something), the following cycles are legal:

Song of the Sea
Beyond the Narrow Sea
Clash of Arms
Time of Ravens
Kings Landing
Defenders of the North
Brotherhood without Brothers
Secrets of Oldtown
Tale of Champions

Anything older than that is CCG-era and is not legal.