Shawn...what is under the beds...concrete, plywood, soil? One option that you could do in addition to all the top dressing/mulching suggested in the other replies would be to remove all the soil from the raised beds and incorporate some hugelkulture. How high is the raised bed above ground surface? You could either remove to ground surface if you have 3-4 foot high raised beds or dig 1 ft or so below ground surface if they are shorter. Then you could fill the hole with any and all organic material you have on hand using the following bottom to top stratification:
firewood sized logs, branches/twigs/smaller woody, leaves, weedy green debris/grass cuttings, kitchen scraps and then put the materials referenced in other posts. You could mix in the removed soil into each layer to minimize open space, i.e., mix leaves and grass cuttings into soil in a wheelbarrow with a hoe/shovel. The woody material would hold
water and also add nutrients as it decomposes. All the other organic matter would continue to breakdown and make the soil better. This is a lot more work upfront but it could pay off with great soil for years to come.
Read Paul's hugelkulture article for more info on this technique:
http://www.richsoil.com/hugelkultur/
Below are pics of my digging out a raised garden and adding organic material...but in the future I would have put the leaves on top of the woody material instead of beneath.