Well my Linksys WRT300N Router was rattling.  Had something broken loose? I needed to find out. So here are the steps to take the router thing apart. along with pretty pictures that you guys really like.

      1. Turn the router on its back and lift and rotate the four feet out of the way.
      2. Gently pry the blue bottom plate off. (Go in from the front and use very small flat blade screwdriver)
      3. Gently pry the translucent bezel off. There are 4 clips holding it in.
      4. Turn the router right side up and do the same thing for the top plate. Be careful not to lose the black button.
      5. Turn the router on its back again, and remove the 4 torx head screws (T05) but beware 2 of them are anti-tamper ( you can remove these with a small flat blade screwdriver)
      6. At this point, the router is well in the nude and you can have your way with it.
      7. Reassembly, do it in reverse. Steps 5 through 1 in order.
      8. (in step 3 be careful its easy to get the bezel on the wrong way.)
      9. Fins!

So what was making the rattling?

A small piece of gray plastic about 1mm x 1mm x 1cm.

I couldn't find out where it came from but who cares? The router works, it was just annoying. And best of all it doesn't rattle anymore. LOL