I breadboarded a minimal PIC18F45K50 circuit.  The LED in the circuit was added to so I can test a minimal "blink the LED" app.  This minimal circuit does not yet include the USB connector, nor powering via the USB bus.  However, it does interface properly to the PICkit 3 programmer (via the 6-pin male header to lower left of IC, rows 21-26 of breadboard), and I was able to blink the LED and set up breakpoints from the MPLAB X IDE.

In case you're wondering how the LED manages to be on despite there being no power applied, it's actually off.  What you're seeing is the camera's flash being reflected!

Added 2/25/2014: In response to comment from hoylegj, here is a zip file of the source.  Really just a few lines in main.c, plus changing the default auto-generated configuration settings in configuration_bits.c to use the internal oscillator.

The Microchip Crystal-Free USB PICs require the PICkit3 for programming.  It's not cheap (compared to TI LaunchPad), but Crystal-Free USB is very compelling, so I got one.

As mentioned in a prior post, the MSP430 series microcontrollers do not support 5V operation.  This made me look for some other low end microcontroller that does, one that I can use for generic projects.

I never thought I would look at the 8-bit PICs (I am definitely looking at PIC32's for other purposes though PIC32's do not support 5V either; also looking at Cortext M0's from various other vendors).  However, I stumbled upon some literature that Microchip now has a line of USB-capable PICs that do not require crystals.  They accomplish this by tuning the internal clock of each chip, then additionally syncing this clock at runtime to the SOF (Start of Frame) packets sent by the USB host.

The idea of being able to experiment with simple USB circuits without needing a crystal was very attractive so I started looking at this line of PICs.  As a bonus, they are available as DIPs.

The ones I'm looking at include the PIC16F1455 (available as 14-pin DIP), the PIC16F1459 (available as 20-pin DIP), and the PIC18F45K50 (available as 40-pin DIP).  Note that the datasheets have "(L)" in the part names, e.g. the datasheet for the PIC16F1455 and PIC16F1459 is called PIC16(L)F1454/5/9.  The L indicates low voltage operation.  There is a PIC16F1459 which operates at 5V, and there is also a PIC16LF1459 that operates at 3V.  This threw me off at first and caused me to order the wrong part (but it was a free sample :-).

I'm going with the 5V ones as I can power them directly from the host (one of Microchip's sample circuits suggests connecting via a ferrite bead) and have one less thing to worry about.  I'll likely use the PIC16F1459 as my mainstay simple microcontroller, the PIC18F45K50 when I need more GPIOs, and the PIC16F1455 if I somehow need very few GPIOs (and happen to have a few 16F1455's lying around).