I'm a huge fan of running web servers in the house - but they don't have to be connected to the Internet to be useful and fun! An Apache instance on my always-on box in the basement [0] serves an incredible number of uses and can be connected to from any computer-like thing on my home network. Old-school CGI scripts can be written almost as quickly as terminal scripts and HTML forms make super quick interfaces. A home web server is probably STILL the easiest way to get files to heterogeneous computers and phones and tablets and...
Edit: ref CGI, there's a few apps on there that do that as well (e.g. fish tank temperature monitor). Nice thing about a small private network is being able to do CGI scripts in bash/whatever without having to worry too much).