I am a proud owner of Google Nexus 7 3G with 32GB.
You all know that it doesn't have a SD slot or normal USB slot. I watched a few youtube videos, showing that you just need an OTG cable, and you can connect any USB flash drive.
1. First - FORGET ABOUT USB FEMALE-FEMALE scenario like this:
It does not work, I still don't know why and I search for reasons. But many people confirm this.
2. Second - NOT all cables work. I went to some shops with the tablet, and the cables seemed good, but they did not work. Finally I bought this one:
There isn't "OTG" word anywhere on the case, but it works. And I think it is too expensive - 5.5€
3. You have to be very careful, because the original cable miniUSB jack is slightly longer:
It clicks firmly to the tablet, BUT the OTG Hama cable does NOT click. May be there are better cables. I will try to remove 1mm of the plastic and maybe post pictures later. As you can see the tablet mini USB plug is somehow under the cover.
4. Software - if you don't root your device like me, you need Nexus Media Importer software.
I was unable to do anything without it, even with ES File Explorer.
The Nexus Media Importer can stream files from your flash memory - movies, music.
It can also copy files USB->tablet.
Vice versa tablet->USB is also possible, but only if the USB is FAT16 or FAT32 format.
5. Other devices
I tried to plug a mouse - it is really funny!
I tried an old GamePad, but it does not work so well. The games don't detect it at all, or misplace the keys!