A Summer of Code project for a C++ enthusiast
I just added a proposal for an interesting project to KDE's Summer of Code Ideas page. It's about kxml_compiler, a tool to automatically generate C++ code for parsing XML data from XML schemas. There is some existing code, but it only barely works. Improving this code to become useful for a wide range of schemas and applications would be a great project. The proposed XML based KOrganier holiday description format provides a nice benchmark for this. The code is used in KDE, but it's pretty much self-contained, so working on it will mainly require solid C++ knowledge. kxml_compiler is part of the Kode suite.
For a student who likes a challenge and enjoys the mind-boggling experience of writing code that writes code, kxml_compiler would be a great project. Don't hesitate, apply now!
There's a pretty mature project that can be use too: xsd. It uses either xerces or expat as xml parser. A useful project would be to extend this to work with libxml2 to add namespace support.
Nativ Qt types
I know this project and it provided some inspiration (The beginnings of kxml_compiler predate it, though, I think). One reason to still do kxml_compiler is to get native support for the Qt types, especially strings and containers. That makes for much more natural interfaces in a KDE environment.