Neighbor Slander Problems (defamation of character)?

Unless you can prove damages, you really have no basis for a lawsuit. You can't sue people for being jerks otherwise. If he is directly haring you, you should have grounds to press charges for harment and/or obtain a restraining order (depending on state law where you reside), but otherwise, there's really nothing you can do other than ignore it and make an effort to get to know your other neighbors. Let them decide for themselves whether you're a nice person or the evil ogre your problem neighbor is making you out to be.