If you have the Creative Suite you can do this in Illustrator and then bring the objects back into Photoshop. In Photoshop, duplicate the objects to a new file, save, and open the file containing the objects in Illustrator. Click on the black arrow selection tool on the tools menu. Go to Window --> Align to bring up the ALIGN dialog box. Hold SHIFT and click on each object to select them all at the same time. In the ALIGN box, under "Distribute Spacing", click the little black arrow under the text, "Align To:". Select "Align to Key Object". One of the objects will be highlighted with a red outline around it. You can use that one or click on another object to make that your key object. In the ALIGN dialog box there is a box that lets you enter the number of pixels you would like your items separated by. Type in a number (eg. 20 px) and then click the "Horizontal Distribute Spacing" button to the left of that box. This will evenly distribute the objects a specified distance away from each other.
You will then need to use the layers palette to drag each object into its own layer. Otherwise when you bring the file back into Photoshop, all the objects will be one on layer. So just click "create new layer" on the layers window to make new layers for each of your objects, and drag each object into a new layer in the layers palette.
When you're finisihed, go under File --> Export to save the file as a Photoshop document. Then open it in Photoshop, group the layers, and duplicate them into your current document.