Unlike the rambling expanse of the Internet, bulletin board systems are enclosed communities where you can swap computer files, indulge in role-playing adventure games, or leave messages and chat with other members. Most are separated from the Internet and must be accessed by directly dialling from your modem into the service - which can be expensive if the service is outside your local call area. There are some BBSs, however, that can be accessed from the Internet, which is a cheaper and easier option. Telnet allows you to use a remote system as if sitting directly at its keyboard. The BBS Corner is possibly the best guide on the Net, with a list of Internet-available BBS services, beginners' guides and a list of Telnet software for most operating systems.
Most bulletin boards are free, but some charge for premium levels of access.
Most offer new users a free trial. Listing names other services, but hasn't been updated for a long time.