Hugin is a great Open Source photo stitcher for OSX, Linux and Windows.
Libccv is an open source image classifier and computer vision library.
It runs on Mac OSX, Linux, FreeBSD, Windows, iPhone, iPad, Android, Raspberry Pi. In fact, anything that has a proper C compiler probably can run ccv. The majority (with notable exception of convolutional networks, which requires a BLAS library) of ccv will just work with no compilation flags or dependencies.
Among lots of other things it has a SIFT implementation
The sources are available on github.
Screenly is a very simple Digital Signage solution for the Raspberry Pi.
Broadcom recently announced the release of full documentation for the VideoCore IV graphics core, and a complete source release of the graphics stack under a 3-clause BSD license. This is good news for the Raspberry Pi community. The release targets the BCM21553 cellphone chip, it should be reasonably straightforward to port this to the Pis BCM2835, allowing access to the graphics core without using a binary blob.
As an incentive to do build a open source video driver the Raspberry Pi foundation will pay a bounty of $10,000 to the first person to demonstrate that they can successfully run Quake III at a playable framerate on Raspberry Pi. This competition is open worldwide, and you can find competition rules here which describe what you have to do, and how to enter.
daten.berlin.de provides access to berlin specific open data sets.