One technique I've yet to try is epoxy--the clear kind, not the wood filler and glue kind. I guess I've always thought it was tricky--you know...bubbles. But Beth's tutorial of a tray makeover (like these from Etsy) makes me want to give it a go. Besides the epoxy and tray--in this case a freaky cat tray--we'll need a secret ingredient to handle the bubbles: A blow torch. (Now we're talkin'.) For the entire tutorial, visit Sawdust and Embryos.
Decorative Mosaic Tray [Sawdust and Embryos]