Here is the very widely used and useful script, tabkey, also known as "the tabscript" or various other names. When you send a message to someone or receive a message it stores their name in a list.
You can pull up that person's name to send a message to them by pressing the TAB key, once or several time. It's harder to explain than to demonstrate. /load the script, send a couple MSGs and then hit TAB a few times. You'll get the idea. Many people can't live without this baby.
Additionnal commands available: TAB move forward through list. ^R move backwards through list. nicklist show names currently on list. addnick add a nickname to the list manually
Note that this binding has been disabled due to conflicts with the screen /LOAD: ^X-^X delete current name from the list