This PiTFT 3.5" is designed to fit nicely onto the Pi Model A or B but also works perfectly fine with the Raspberry Pi 2 Model B or Pi 1 Model B+ as long as you don't mind the PCB overhangs the USB ports by 5mm.
Uses the hardware SPI pins (SCK, MOSI, MISO, CE0, CE1) as well as GPIO #25 and #24. GPIO #18 can be used to PWM dim the backlight if you like. All other GPIO are unused. There's a 2x13 header on the bottom, you can connect a standard Pi GPIO cable to it to use any of the other pins ask you like.
Best of all, it comes fully assembled and ready to plug into your Pi! You can use this as a display for running the X interface, or pygame. You can also have an HDMI display seperately connected. There's four mounting ears that can be used to attach the display & Pi to a bezel, or snap them off with pliers (they're perforated) for a slick exactly-the-same-size-as-a-Pi look.
Adafruit has created a custom kernel package based of off Notro's awesome framebuffer work, so you can install it over your existing Raspbian (or derivative) images in just a few commands. Their tutorial shows you how to install the software, as well as calibrate the touchscreen, display images such as from your PiCam and more!