Which SD card reader to buy from Ebay?

They are all in the range of 1-2 dollars. I would go with this one: www.ebay.com/itm/331468332421
Or this one www.ebay.com/itm/111536128198 (do I really need all those pins?).

What would you recommend?

looks like the cheaper one does also 3.3V.
And it has a link on the backside, maps to http://www.lctech-inc.com/

you need 6 pins. 4 for spi, 2 for power == 6.

For about the same price you can get one with a level shifter rather than a resistor network to handle the 5v to 3.3v logic.
Like this one. http://www.ebay.com/itm/Micro-SD-Storage-Board-Mciro-SD-TF-Card-Memory-Shield-Module-SPI-For-Arduino-EC-/221744960646?pt=LH_DefaultDomain_0&hash=item33a1079486

The ones branded Catalex work well when they are alone on the spi bus. The early units may have had problems working well with other devices on the bus because they don't release MISO. I don't know about the new ones labeled v1.0

I believe that others have had problems with the lctech units. (several...) SD just, simply, not working! [SOLVED, tnx fat16lib] - #11 by fat16lib - Storage - Arduino Forum

What would be a good SD card reader module for 3,3V projects (-> module with no level shifter and no voltage regulator).

You just need a card slot. This one -- SparkFun microSD Transflash Breakout - BOB-00544 - SparkFun Electronics -- is just the card slot conveniently attached to a board for you.

jboyton:
You just need a card slot. This one -- SparkFun microSD Transflash Breakout - BOB-00544 - SparkFun Electronics -- is just the card slot conveniently attached to a board for you.

Thanks you for the link - that's exactly what I'm looking for.

But Sparkfun is a boutique, so I try to avoid them. Unfortunately I haven't found this device on eBay :slightly_frowning_face: