Making a blogging engine in C would be very informative (though difficult).
[1] https://github.com/spc476/mod_blog
[3] https://github.com/spc476/CGILib
[4] gopher://gopher.conman.org/
The best part is that where stores his posts. SQL? Nope. NoSQL? Nope. Plain text files? Nope. Fucking LDAP. [1]
[1] Source: http://blog.fefe.de/?ts=a8d61c27