The USBtinyISP is a kit for a USB-connected AVR compatible ICSP programmer:
On the left are two cables, with 6-pin and 10-pin ICSP plugs, respectively. Inside is a pre-programmed ATtiny chip plus some level converters for use with 3.3V hosts (do need to remove a jumper for that).
Built into avrdude by using the “-c usbtiny” option. No need to specify port or baudrate (unlike some other programmers). To make this the default programmer, I added this line to my ~/.avrduderc:
default_programmer = “usbtiny”;
This little device works really well.