Now when I plug in my phone via USB I get only my external memory music files. I have a folder listed 'playlist'.
How I got a CD or music on my phone was through Windows Media Player. Windows Media syncs right up with the phone if it is plugged in using the USB cable.
Otherwise, the correct folder to put the music under is 'playlist'.
I found the same issue... I make ringtones with Audacity and export the mas mp3...when I try to put them onto my phone via usb, it only shows the external music folder. I treid going to settings and tools, tools, and usb mass storage and it shows the other files on my phone like my sounds and my pics, but when I put pics and sounds into those files and unplug and restart my phone, they don't show up onto my phone.

You're not going to be able to transfer .mp3 files with USB to get ringtonoes. The .qcp files are an option but I've found that the quality is poor.
There are two ways to transfer your own .mp3 files as ringtones. The first is to email them to your phone [
number@vzwpix.com] as an attachment. The other option is to use bluetooth. Check
http://www.samsung-reality.com/how-to/how-to-easily-transfer-ringtones-from-your-pc-to-your-phone/