I have LCSOFT SD modules, link: http://www.lctech-inc.com/Hardware/Detail.aspx?id=0c3b6f7a-d101-4a60-8b56-3abfb7fd818d
They take either 3.3V or 5V. I have only run them on 5V. The power level circuits are built in and raised some eyebrows but they work. Hardest part for me was getting up nerve to try but I got a good price on 3 at eBay.
Also make sure the SD card is formatted FAT-16, the most compatible. And IMO the SD-Fat library is better.