I have an older edition that uses hexagonal port tiles rather than the new ports so the Plastic Catan Board doesn't work for me. I use blue drawer liner (cut into two strips).

http://www.amazon.com/gp/product/B000BQK0EO?psc=1&redirect=true&ref_=oh_aui_search_detailpage

Pros: Keeps tiles from moving. Folds/stores easily in box. Looks like the ocean. $4. And, just a personal preference, I like my tiles touching rather than having the road "moats" in between.

Cons: Doesn't help transport board. May not help your crack situation. Doesn't help spills. Doesn't help errant dice rolls. Slightly ghetto.