Here's my list of additions/enhancements. There's plenty more, but this will do to start:
Flexible vertex formats - move away from 3 fixed vertex formats
Material system - collapse filter modes to a single flag, etc
Scenegraph - reduce redundant node updates, etc
Hardware skinning
PVS system - no more using Octree for everything
Postprocess
Capable of fully shader-based rendering for DX10 and above.
I think a DX10/11 driver would be cool, like sio2 said. I also think that animation blending, and simultaneous keyframe and morphing animation would be good too.
Yeah, many of these things are pretty good things to have. But most of them won't fit into the GSoC scheme, where a student without much knowledge about Irrlicht internals will have to do some implementation. Hence, the driver ideas are listed on the Ideas page, and also some effect stuff (Decals would also be a good idea, I'll add it). But many other things, such as flexible vertex format, requires changes in almost all places in Irrlicht. This is not possible for the intended scenario, at least for people without good knowledge about Irrlicht's architecture.
If you have some good literature for those topics, e.g. PVS, we could probably also add them or amend the already existing ideas.
I am not quite sure if this qualifies for a GSoC Idea, but what about an Irrlicht "Public Relations" Project.
Creating a new Website which integrates the Forums
give the users abilities to share/upload their Projects in a designated area.
Better intigration of the wiki
better intigration of the svn website
Remove duplication of content and enhance the usability and interface of the Community
Better integration of things like Screenshot of the month. Just look at the "Screenshot" section on the main page. Those are screens from up to irrlicht 0.4 which are presenting our engine to potential new developers. Not a good idea, imo.
I never seem to be able to find the adress to the IRC, even though I know it exists
Creating a new tutorial series, updating the old ones. Some examples on the webpage still use code from old irrlicht versions (at least so I have been told by some guys I directed towards them)
The tutorials link directly to the API page, which means a change in layout, even though you are kind of still on the same page. Which is confusing
The Layout of the main page. It shouts "we are old fashioned and missed the step into the 21st century"
It all appears to be cluttered and patched together from several open source projects at the moment. In my opinion one of irrlicht's greatest weaknesses is its presentation to the public.
I have lot's of ideas for such a project and I think it can really help attract "professional" game developers towards the engine which, in the long run, means more contributions from qualified and experienced developers.
As I said, I am not sure if this qualifies since it's not working on the engine itself. But it's still writing Code and not "just documentation work", which is prohibited in the GSoC FAQ.
Well, I hoped "Creating a Web-Community" would count. Since in web development I could make a good contribution. (read, not using Wordpress/Typo3/"insert your favorite CMS here" but actually planning what this community needs and creating that from scratch).
Using a CMS is easy, but they always are so loaded with features no one ever uses. I am a do it yourself guy :p
Well, then I have to think of something more Irrlicht related.
Ok, submission as a mentoring organization has been submitted. I hope we are chosen this time, so prepare to take one of our suggestions as project - in case you are eligible of being a student at GSoC.