I just got the IOGEAR SuperSpeed USB 3.0 SD/Micro SD Card Reader / Writer yesterday and it’s the fastest SD card reader i have ever seen. This was very cheap too, you can get it for around $15 from amazon.
I was able to get 20MB/s write and 30MB/s read speed using a Patriot LX 16GB SD card on a USB 2.0 port on my MacBook, I properly could get a lot faster read speeds on a USB 3.0 port.
Good work IOGEAR!
You can read more about this product at http://www.iogear.com/product/GFR304SD/
Update:
I have tested this card reader on a windows 7 machine with a USB 3.0 port.
I got 63MB/s read and 38MB/s write speed which is really cool.