cusp - I'm not a big fan of Eclipse (it just consumes more resources than I'm willing to grant an IDE), but this is quite nice. Namely, an IDE for Lisp that builds on the usual integration tools and thus creates an interactive Lisp environment - but with the typical Eclipse features for the editor and source navigation. Looks good. And apparently there's also a simple installer (which includes the appropriate SBCL) that also supports OS X. Maybe I should download Eclipse again ...