This paper presents the RCXLisp library, an extension to Common Lisp that allows students to investigate a broad range of artificial intelligence and computer science topics using the LEGO MindStorms® platform. The library supports both remote control and on-board programming of MindStorms robots. It also supports targeted communication between multiple LEGO robots and command-center desktops. The package is the only one to be integrated into most popular Common Lisp programming environments. This paper also summarizes student experiences with the package over the years 2000-2003 in an Artificial Intelligence course.