Nnexxus: Yes, the SD slot is a great feature on the Clip+. I have bought a 8GB model, and after a few months when I ran out of space, I added a 16GB SD card. I still have plenty of free space despite putting my whole music library on it. And carrying 24GB worth of music in a device the size of a lighter is great :-)
ChaunceyK: Can you tell me what I'm doing wrong here? I've got the card, I can put music on the card when its in the adapter & plugged into the computer. But the card reads empty when its in the player itself & refreshing it doesn't pick it up either. :-(
Sorry for the delay, I'm a bit busy right now.
I'm not sure what your problem is, but here are some tips that might help you. I use my Clip+ this way and it works fine.
First, you have to understand the difference between MSC and MTP. Those are the two USB modes supported by the Clip+. Basically, MTP is specific to MP3 players (and cameras, and other devices). MSC is the standard external storage format, like USB keys and memory cards. You should choose which standard you want to use (I suggest MSC for better compatibility), set up your clip+ to use this format instead of the default "autochoose", and stick with it. Those two formats are almost like 2 partitions on the internal storage : if the Clip+ is in MTP mode and you plug it in, the computer won't see the songs that you have transferred in MSC mode, and vice versa.
Once you've transfered your songs, the player should update its database when you unplug it. If the database update crashed, try to replug the Clip+ to your computer, change something (add/remove one song, for instance) and it should re-update. Once the database updated successfully (it can take some time depending on the number of songs : mine takes up to 5-10min) you should be able to navigate your library. If not, try to navigate through your database "by folder" on the Clip+, to see if the files are present in the filesystem.
Then, to use the external SD card, I suggest leaving it in the SD slot of the Clip+. You shouldn't need an adapter, except maybe if you feel the transfers are faster, but if you run into trouble try to leave the card in the Clip+. When you plug the Clip+ to your computer in MSC mode, it should appear as two drive letters in windows : one for the internal storage, the other for the SD card. Just drag and drop some music on the SD card, exactly like you did for the internal memory, and you should be fine.
Note : I had some trouble with Windows 7 64, it did not detect my SD card when it was in the Clip+. Putting the card in an external adapter worked fine. If you run into the same problem, let me know and I'll try to remember what I did to solve this problem.
I hope this helps you.