N-Krypt is a freeware, effective text encryption program. It allows a user to enter any amount of characters, which can then be encrypted. The other user can then easily decrypt the message. It is fast, free, and small.  
Note: Visual Basic 6.0 SP5 Run-times are needed for this. Windows XP (Home or Pro) users already have this, do not worry about it.  
It can be downloaded from http://download.microsoft.com/download/vb60pro/Redist/sp5/WIN98Me/EN-US/vbrun60sp5.exe