As a programmer, things I love non-programmers to do:
A bug report means absolutely nothing if I can't reproduce the bug. If I can't reproduce it it means I can't prove that I've fixed it. A bug report I got in the past:
Subject: [SEVERE BUG] Crash after 10 minutes
I mean, what am I supposed to do with this? After 10 minutes it's still working for me...
Things to include:
If it generates a core file, I will want a backtrace. This is easy to get with gdb(1):
$ gdb ./program-that-crashed ./core (gdb) bt full
Also, I'm a programmer, I suck at documentation. It's far too easy to think "that's obvious", or just use bad terminology or spelling. What really helps is getting someone who isn't a programmer to give the documentation a once over and send in suggestions. The WlugWiki is a great example of this. If someone asks me something I usually try and get them to wiki it. Why? Because if I have to wiki everything I'm asked, I'm gonna give up answering questions, and people tend to wiki things from their point of view ("I want to do this") as opposed to mine ("this is how the program works"). I always go back and check what people wrote to check it for accuracy and for clarifications.
If you have a problem and spend time researching it and find the answer, please wiki it, so that others can benefit from your help, or more importantly in 6 months when you're trying to remember how you did whatever you did you have a reference. Writing up HowTo documents in the wiki is surprisingly addictive, as is cleaning up old pages in the wiki. Perhaps you might like to start at WantedWikis...