Frequent tipster Leonid Nemirovsky sent us a tip showing how to use a command over and over again.
If you need repeat a command many times, for example command FILLET, at the command prompt, type MULTIPLE, then specify command (in our case) FILLET.  Then supply input as usual for FILLET command and select as many lines (plines etc) that you need to FILLET. Cancel when done.

Notes from Cadalyst Tip Patrol:  This is a great reminder for those commands that do not have a multiple option.  Fillet does, but it is a great example.  Good tip.
Tested in AutoCAD 2009