The anime ends with episode(s) 166-167, which roughly corresponds with chapters 345-356/volumes 36-37. Some actual "wait wait WHAT OMG" plot development occurs in the manga after the anime ends, which kills me. At least the first 3 of the 4 movies are loosely in canon with the anime but not the manga. The manga is currently up to chapter 503/volume 51 in Japan, making Inuyasha Rumiko Takahashi's longest-running series (not incidentally, she is one of Japan's richest women). Someday my corpse will be found buried Scieszka-style beneath my collapsed shelves of Inuyasha manga. Bookmooch.com and Half.com have helped a lot.

Ear-Tweak is an excellent information resource for the series, including the lovely cracked-out soundclips collection.