Laurent Demailly and Peter Pletcher
Native byte-code compiler and remote control library.
The TCL RCX compiler has double-edged functionality: it can either compile a TCL script into RCX byte-code, or it can remotely control the robot via either a script or an interactive TCL shell. If TCL is your language of choice, this is the optimal solution. There are two versions available: Laurent's (at demailly.com) appears to be the original of the two. However, neither appear to have been updated since 1998.