I had my first contrib module accepted on drupal.org! It's nothing flashy, but it was a quick solution to a problem I have on this site quite a lot: spam. I want people to be able to comment on posts if they want to, but for a site like this where a user is unlikely to keep coming back I felt it was overkill to force someone to register with the site in order to post comments - so I've allowed anonymous comments but they require admin authorisation before they're published.
This obviously brings a lot of spam comments - maybe 10-20 a day - which isn't a big problem. I get an email telling me someone has posted a comment, and I can check if it's genuine. If it's genuine I'll go in and allow it, if not I'll leave it and every week or so clear out the spam comments. There's plenty of spam solutions out there, I personally use Honeypot, which prevents an awful lot. There's also things like reCaptcha, Spamicide and Mollom - but none of them are 100%, some spam is going to get through eventually.
The Comment IP module I've written gives you an overview of the IP addresses of comments which have passed through your filtering system, so at a glance you can see if there are any persistent offenders - and then you can block them! You can also do the same if you're getting abusive/harrassing comments from one location also (something thankfully I've not had a problem with).
So there's my first contrib module. Now I've got one accepted I'm keen to keep contributing!