One area of open source development that really lags is the area of mobile or cellular phones. (They're mobile in England, cellular here, two peoples still separated by a common language.)
Mobiles are the most popular computing platform on the planet, yet Sourceforge lists barely a hundred projects specifically for mobile phones.
The reason, of course, is that mobile environments are highly proprietary. Most run on proprietary operating systems, and carriers add (or subtract) features and instructions for proprietary reasons.
Many such projects come from market failures. Among the more popular is the floAt Mobile Agent. It's designed to link your Windows PC to mobile phone data (which sounds neat), but it currently supports only the Sony Ericsson feature set. The project lists 29 developers and four project managers. Geekzone compares it to PhoneKing, a Windows Mobile program.
As much fun as it may be to tweak Microsoft, or dream of open source breaking the Microsoft monopoly, the fact remains that mobile monopolies are tighter, bigger (in terms of units) and under much less threat from open source programmers.
Care to change that?