CGTERM by Per Olofsson is an excellent Commodore Graphic terminal emulator which runs in Windows, Mac OS X, and Linux. You can download it at www.paradroid.net/cgterm/ ... Unfortunately, it's a Telnet-only program, so it can't be used for dial-up connections.
However, Greg Pfountz, the author of the software that I'm running on my dial-up board, also wrote a terminal program for MS-DOS in 1991 called the C64 Color Terminal Emulator. Unfortunately, not all modems are supported with this program. External modems work best; most "WinModems" will not work. You can download this program at cottonwood.servebbs.com/C64TRM5B.EXE ... Some have had success running this from a DOS window from within Windows. The best thing is to just try it out and see if you can get it to work. Be sure you know what COM port your modem is running on, and set the config for the terminal to use the same port.
I thought this information might be useful to people wanting to call Borderline BBS who don't have Commodore hardware to call with. It's also possible to call using the Commodore terminal program of your choice from within VICE. Of course, if all else fails, just call using any ASCII-capable terminal program.