This is a remix from bgill's Micro SD Card Holder. I noticed a few people asking about a standard SD card size and found myself in need of one as well. This holder is 45mm wide and about 38mm tall with the cap on. It holds 6 standard size SD cards. The example in the images was printed in ABS and the cap is really tight. I haven't tried it in PLA to see how that does but if it gives anyone any troubles just let me know and I'll do some resizing.
[UPDATE 02/08/2016: As suspected, the lid is too tight. Thanks to mzdxjx, I've added a v2 cap stl that is 1% larger and should fit much better.]