There's a new Mac app called Serial available on the App Store. Full disclosure- I wrote it. We got tired of having to find and install drivers for different serial adapters and devices we have here in order to administer Cisco switches, so we wrote our own terminal that uses its own built-in drivers for the most common chipsets available. There's a free demo available.
Also, as of Mac OS X 10.9, Apple began shipping their own FTDI driver. So, if you're using a USB-serial adapter that uses the FTDI chipset (many of the higher-end adapters do), you don't need to worry about installing drivers and can use the built-in screen command in the Terminal to access serial ports.