Hey all. I replaced the paper in my wet palette today and thought I'd snap a few photos and tell you how I made it. for those that aren't familiar with them, wet palettes use wet sponge materials in a sealed container to help keep paint moist and useable. It's a good way to keep mixed colors going longer, and even lets you store them overnight without drying out. I think they are a big help when using paint from dropper bottles, and help with blending techniques in general. A lot of craft and art places sell them, but my way is super cheap and just as effective.
You will need: - Parchment paper: I'm not sure where this falls in the realm of wax paper, but it's a non-stick paper baking product that lets a little moisture through and makes the whole thing work.
- Kitchen sponges: These are super cheap at the grocery. You want the cheapest kind with no scrubbing pad or other futuristic enhancements.
- A more or less airtight container: I used a plastic container that grocery lunchmeat comes in. Tupperware and whatnot would work too, but if you do it my way you get a sandwich out of the deal. The main thing you are looking for is something with a decent seal that's not too deep.
I cut my sponges to fit my container. You could certainly get by with just one, but I wanted to maximize my surface area to keep from both having to change the paper often and/or having areas of paper with no sponge underneath. 
All that's left is to cut a small piece of parchment paper to fit over your sponges, and you are good to go. You want the paper to lay flat, so you may have to roll it up backwards to even it out after being on the roll. Once it gets damp it will adhere pretty well with no problems. Put your paint directly onto the paper and work from the palette-- you'll find the paint stays nice and smooth, and is slightly thinned from the watery goodness. When you are done painting, slap the lid on and your mix should be more or less fine when you get back to it. I think wet palettes are a great way to save time, effort, and frustration, and make trying new painting techniques a lot easier. I hope this was helpful, and if you have any insights or questions be sure to drop us a comment.
-Boltergeist