There are a couple of ways to "sharpen" semi-blurry images. You won't be able to completely make sharp images out of out-of-focus images, but you can try.
1. Under "FILTERS" you can go down to "SHARPEN" and select "UNSHARP MASK" this will pop up a new window. Use the slider to desired effect.
2. You can push the letter "R" on your keboard and it will select a tool on your tool palette that looks like a water drop. If you click and hold this button you will get a couple other tools to choose from, one of which is the "SHARPEN" tool. Use this tool to sharpen specific areas of the blurry image. If you're in Photshop 7.0, your strenght and brush sizes for this tool will be docked at the top of your window.