I cut a slot with a keyhole bit like Roly showed, but on a router table. I set up stop blocks on either side of my fence to align marks I have made on my blank. Raise the bit to desired hight. Adjust the fence for the distance from the top of the blank you want the slot. I align the blank against one stop block, raised above the bit, then lower the blank to the table. I stop the router waiting for the bit to come to a complete stop. Then lift the blank off the table and move the blank against the other stop block carefully lowering the blank over the running bit. Once the second hole is cut, carefully move the blank against the fence to the next stop block. Turn of the router till it comes to a complete stop, then lift the blank off. You now have a slot with a screw hole on either side.
If I have time this weekend, I'll take some pictures with a tutorial on how to do this.