I quickly discovered that a particular piece of software I used daily wasn't really being maintained all that well, despite the fact that there were several contributors listed on its home page. A few dozen bugs reports (some even including patches!) had come in, yet only a few had even been acknowledged.
This seemed like exactly the type of project I was looking for -- something that I used every day and could help improve. I sent an e-mail to the developers stating that I was going to be devoting some time to the project, sending patches in for the bugs, etc., and asking if there was "anything I should know" before jumping in. I spent a lot of time reviewing the previous discussions on the mailing lists, examining their previous commits to see how they did things, and so on.
One of the developers finally replied -- about a week later -- and asked for my SSH key. I sent it to him and he quickly gave me commit access, thanked me for the assistance, yadda yadda.
I closed out umpteen bugs, responded to previously unanswered messages on the mailing lists, and sent patches to the developers list asking for feedback before I committed anything. Having received no responses, eventually I committed all the changes and pushed them into the master branch. Questions that I had to the other developers went unanswered, just like all the previous bug reports and user-submitted patches had.
After a while, I just quit spending any time on it. Perhaps a month after my latest fix, I look at my e-mail one day to see a flood of notification e-mails about commits. The lead developer had reverted every single commit I had made. I was looking for -- expecting -- some explanation but never received one, even after I finally directly asked, "WTF did I do wrong!?".
Nothing. No response, to this day. I eventually said "fuck it", deleted my private key, unsubscribed from the lists, and moved on. I just looked and there are still bugs open today that were open back then.
The sad part is that this piece of software is fairly widespread and a part of all of the major Linux distributions, installed by default on many of them. I think there's been one, maybe two, "releases" in the last five years.