I'll echo the recommendations for the Paizo maps. They actually have two lines: the Paizo Flip-Mats, which are two-sided poster maps with artwork and grids (some of them detailing pretty specific locales, but others more generic like what you're looking for: Hill Country, Woodlands, Deep Forest, Winter Forest, Falls and Rapids, and so on), and the Paizo Map Packs, which are one-sided 5" by 8" cards that can be lined up (often in multiple ways) to form larger maps. The city ones are handy to create different city areas with the various cards moved around in different setups, but they have all sorts of different types of terrain in their Map Packs line as well.
Johnathan
Johnathan