For prototyping I'm going to need a breakout board for the micro, so I had a look at what I could find. All the breakouts I could see for QFP64 pinouts had holes on all four sides, which is unsuitable for breadboards. I guess jumper leads would work, but still... So I designed my own. In fact, I went a step further and made it a bare-minimum dev board for the STM32F373 as well – it has the decoupling caps for power and the reference voltages, a power setup so that it can be powered off a single rail, and a programming header. But don't install any components, cut the net ties in the ground, and it is simply a QFP64 to DIP breakout. It has a standard DIP pinout, and fits a breadboard nicely – well, if spanning two slots (i.e. 1" wide) and taking 32 rows is "nicely"!