Monster Geographica: Forest is a pocket book-sized compilation of forest-dwelling monsters compiled from numerous OGL sources, updated to v3.5, and organized by CR. From the publisher's website:

Monster Geographica: Forest is a 208-page pocket reference packed with 200 monsters from over twenty different sources (both converted 3.0 and selected 3.5 monsters). Conveniently organized by challenge rating, this affordable resource of forest monsters is perfect for random encounters, adventure building, and campaign design.