My friend is learning C (and some computer science), I've pointed him to "Learn C: Build Your Own Lisp" and some frequently shared online courses but I'd love to share a bunch of small (fun) C projects with him that do a good job at showcasing the language. For example Kilo from the creator of Redis https://github.com/antirez/kilo
I find myself reusing components in several projects, then test & documentation is even more important of course. I formalised a layout for these components as "C99 sushi", there are a few here: <a href="http://soliton.vm.bytemark.co.uk/pub/jjg/en/code/c99-sushi/" rel="nofollow">http://soliton.vm.bytemark.co.uk/pub/jjg/en/code/c99-sushi/</a><p>Mostly maths stuff, possibly interesting?
i recommend doing forum software with cgi. it's fun and challenging. After that there are plenty of stuff you can do with gtk.<p>over the years I have a bunch of small gtk c applications that ranges from mp3 players to rss readers.