We had this exact problem, and got tired of using net send. Two of us wrote a program called t++, and we just finished version 1.0 after a year of development. It features:
- Tabbed Chat - have a tab for each of your peers
- Encryption
- Tells you when the user is typing a message - their name goes bold
- Tells you when the user's box is locked - their name goes italics
- Saves peer and tab configuration
Go here:
http://hms.dyndns.org/t++