Editor's note: This description was updated on August 29, 2011.
There has probably been an Offset to Layer command available since AutoLISP was introduced. Autodesk eventually included this ability into the core Offset command. All these years later, Kent Cooper has still managed to improve on this idea.
This version of Offset to Layer will allow you to offset to any layer, not just the current layer or the source layer. You can even offset objects to locked layers. To get started, load the LSP file and type OL on the Command line. Enter the offset distance (or Through), type in any existing layer name, then finish the command. If you enter a layer that does not exist, you can try again. This routine also remembers the last used distance, separate from the distance last used by the core Offset command.
AutoLISP fans, check out Kent’s code, which is well documented with comments.