<p>I've been wanting to program for the Plan 9 operating system for a while. I'd really like to play around with a web app there. Of course, the only language I know for Plan 9 is C, and that doesn't seem ideal for web development. I also understand that it doesn't run apache or mysql either.</p>

<p>What is the best way to start coding web apps on Plan 9?</p>

Check out Kenji Arisawa's
Pegasus
(
paper
) webserver for Plan 9.
Plan 9 may have a reputation for being C-only, but several langauges, including Scheme, Ruby, Python, and Perl have been ported. Check out the
Contrib Index
for the code.
Finally, start reading the Plan 9
white papers
so that you can understand its philosophy. If you want to do net-related things, the file protocol
9p
is essential.