There are many programs out there. For PCs the most popular is mIRC, which is available at http://www.mirc.com. The program is shareware, but can be used for free indefinitely.
Thank you for trying out mIRC. mIRC can be downloaded freely and evaluated for up to 30 days. If after evaluating mIRC you find that you like it and wish to continue using it, you will need to register your copy.
How do I register mIRC?
You can register mIRC by clicking on the Register mIRC button on the right.
Not entirely true, [I can say that as a user of the latest version for more than 30 days]
When the 30 days have expired, you do get the same "Register" and "Continue" options with the continue option greyed out for the first 5-10 seconds as in the older versions, with which you simply click continue after it arrives.
You also get a couple of times when you get "Register" and "Exit" as your options - when confronted with this, I restart the program, [sometimes twice] and then get to the "Register" and "Continue" again