It might have taken nearly an entire year to arrive, but the official touch display for the Raspberry Pi is here. Fortunately, the long wait isn't being met with an overpriced product - that'd be rather atypical of the Raspbery Pi foundation. Instead, you'll be able to get a very capable 7-inch touch screen for about $60 USD.
With a resolution of 800x480, this is far from being a "high-resolution" panel, but the feature set more than makes up for that. It takes advantage of the RPi's DSI connector, which allows users to continue using the HDMI port for other purposes - and it is possible to use both the touchscreen and external display at the same time. Another cool perk: the chassis can be had in a variety of different colors, including purple:
It should be noted that the frame itself is a £10 add-on. Other perks include being able to power the touch display from the RPi itself (meaning, just one power connector), and being able to affix your RPi itself on top of the RPi's PCB, as seen in the shot above. For a DIY solution, this sure is an elegant one.
For a breakdown of what this touchscreen is capable of, and an overview of all of the different configurations you can use it in, I'd highly recommend checking out the video above.
All told, if you purchase an RPi, its power supply, and this touch screen, it will run you ~£83. Based on the quote of $60 for the touch screen itself, the kit should run about $100~110 in the US.