i downloaded some texture packs and tried to use them. i zipped them and put then in the textures folder, then i opened up minecraft and chose the texture pack, and nothing changed. the icon for it was grey and the same as the default icon.
Did you put the folder with the textures inside a zipped folder? If you did that may be your problem the terrain.png(along of the other folders and images) should be directly in the zip, not inside of a folder inside the zip. This might not be your problem, but I know it's happened to me and I hope it helps.
No...if you own a mac, like I do...you download the latest Xau's HD texture pack fix..it's the easiest way to download the packs. Watch my tutorial if you want to....but it's self-explanatory. You don't unzip the file, you leave it, put it in your desktop, then open the fixer up, and follow the directions. Boom.