1:1 female jumpers are handy for connecting pin headers between two devices. We use them with the Bus Pirate, Logic Sniffer, and Bus Blaster JTAG programmer. These were out of stock for a while, but Seeed has them in stock again at $5 for a wad of 50.
I also added 1:1 male jumpers to my kit to make it more versatile. Sometimes my friends’ boards have female headers, so I plug a male jumper to a female jumper to be able to connect my BP or OLS to the circuit :)
I like to use the 1:1 female jumpers together with these lengthened double male headers also for prototyping on a breadboard: http://iteadstudio.com/store/index.php?main_page=product_info&cPath=10_12&products_id=116
They make better contact than the 1:1 male jumpers.
I’m sure they make great contact, but don’t the 100 mil headers stretch out the spring-loaded contacts inside a breadboard? That’s a question I’ve often wondered about, but have never found an answer.
No, I don’t think so. I used them for quite a while now, and the spring contacts still work fine. When forcing a 7805 linear regulator into the breadboard, that stretched the springs a bit.
If you have m/m and f/f jumpers back to back you can jumper some leaded SMT parts onto a 0.1″ plug-protoboard. Now, if only they sold m/f jumpers instead ;-)
take one M-M jumper, add one F-F jumper, and lo-and-behold, you have a workable M-F jumper !