hi, welcome to the forum.
it could be rather difficult to communicate with this SD adapter, as you would need to implement a usb host controller protocol.
how does usb work?
no idea. the USB people are NOT forthcoming with specs etc. they want $4000 a year or something.
it would probably be easier to interface the SD card directly to the microcontroller.
as far as im aware, SD cards use SPI which is synchronous, meaning they do not have a MINIMUM speed. im not sure how the SPI is implemented for SD.
if you are new to microcontrollers and the like, i would start with something more simple.
a helpful tutorial i learned a lot from.
**broken link removed**
this uses the PIC16F84 PIC microcontroller made by microchip. it is very basic, but useful.
if you want something with more capability, you can use a 16f628, 16f88 or a 16f877.
My programmer is the velleman K8048 kit programmer. it's simple, but lacks software control of the VDD line(is controlled by a switch instead). this is ok, but you could find yourself in an annoying situation if you accidentally disable the MCLRE bit of the configuration word.
that is the PICmicro by microchip.
there are other MCUs out there such as the parallax propeller(VERY weird architecture, 8 cores with a total of 160 MIPS) or AVR(dont know much about them).
you could also try an 8051(will require an eeprom programmer, no internal flash) or an AT91(same situation).
PICs are the least powerful in terms of memory and speed, but there are the parallax SX MCUs, which run the same machine code as the PIC and are MUCH faster, but they need a different programmer. PICs are also the cheapest.
there are also the BASIC stamps, which are circuit boards that contain an MCU, memory, a voltage regulator and other stuff. the MCU interprets BASIC code. these are generally slower than the PICs, but easy to program.
personally i would go with a PIC or a propeller.
as far as PCB design goes, i dont really know the best program. ive heard a lot of people use EAGLE. i use gEDA PCB because it runs on linux.
I get all of my parts from maplin(in the UK) and farnell.com
about voltages:
3.2v circuits can be interfaced to 5v circuits via a "level shifter".
EDIT: on programmers: you can build an "EL Cheapo" programmer for PICs. if built correctly, it shouldn't be any better or worse than any other programmer.
for the development environment for PICs, you can use microchip's MPLAB, or, if you are using linux, you can use pikdev.