As expected, no luck so far with the VUB300. The problem is that I don't have a clue where to look.
Testing with a multimeter, D0-D1-D2-D3-CLK-CMD from the SD socket goes to the corresponding pins of the VUB300.
I did put all the components on page 10 around the chip and checked that there is 3.3V on pins 6,14,22 and 36.
I then cut a spare USB cable and attached this to the chip (D+, D- to pin 2 and 3, ground and shield together to the GND).
I'm not 100% sure about the USB pinout. On page 12 there is a description of a USB socket block. It seems that I have to put 5V on the vBUS pin (red wire on most USB cables), but since the USB port of the computer already supplies 5V, I thought I didn't have to connect this? I didn't put the components for that power supply either. I have put a 1µF elco between the GND and vBUS, although I don't run the vBUS pin anywhere on the chip.
Regarding USB+ and USB-, I've connected the wite wire in the USB cable to USB+ and the green one to USB-. I'm not sure if this is right.