The NCSA Telnet seems to be the most popular.
Black Lizard
I assume this another of those headless posts where the OP is missing in action?
Black Lizard is right about NCSA Telnet; there is also a program dedicated to telnetting into an IBM mainframe which expects you to be using a dumb terminal with keys you ain’t got (“Erase EOF”, anybody? How about “Clear Screen”??) – tn3270 lets me run my antediluvian account at SUNY Stony Brook and speak VMS.
I am closing this because it is a headless clone of [Telnet Equiv. for Mac?](http://boards.straightdope.com/sdmb/ showthread.php?s=&threadid=107310)
DrMatrix - General Questions Moderator