Just a word of warning:
I've been using a cheap FTDI-USB adapter from China (ebay) that has a 5V-3.3V jumper on it. With the jumper set to 3.3V, I connected my 3.3V pro-mini to it with the nRF24L01 module still attached. I spent a few minutes with it hooked up that way, trying to get my node to talk to my gateway, and suddenly my nRF24L01 module stopped responding altogether. I swapped it out with another one, and after a few minutes that one stopped responding too. I double and triple checked my all wiring, then I started poking at it with a multi-meter...
...and I discovered that the FDTI-USB adapter was giving me 5V on the VCC pin! It didn't matter which way I set the jumper, VCC was always at 5V. Then I checked another FTDI-USB adapter I had lying around. That one had a switch instead of a jumper, and it turned out the labels on the board were reversed - setting it to 3.3V was actually 5V and vice-versa!
So just be aware, and double check the voltage before you trust those things.
