You cannot take a specific feat more than once, unless the feat specifically says you can. Note however that some feat chains have two (or more) feats that share the same mastery rating: these are still two (or more) different feats.

For example: Improved Trip has a base mastery (which is set at mastery 2) and two expanded mastery 2 feats (one finesse, one power). You can take all three of these feats if you wish, as they are all different feats.