Another thing I've created is Debian BTS: cleaning up. I use this link in my mails to the Debian BTS for my stable RC cleanup efforts, or general proper closing of bugs that aren't getting archived. Through the help of UDD I've created me helpful overview pages of bugs that need attention for this.
The third thing I've created is Package Maintenance. If you are a fan of one of the packages I maintain and want to thank me for taking proper care of it, feel free to also click this one. Please be aware that this shouldn't be seen as an Upstream appreciation—if one of the projects I package for Debian uses flattr themself then you should definitely (also) consider flattring them for their own.
About Upstream projects that use flattr: One of the packages I invest quite a lot of effort into started using flattr: wesnoth. They have put the flattr button on their entry page at wesnoth.org, here is the direct link to their first and general thing: The Battle for Wesnoth.
Please be reminded that the things you did flattr in a previous month can again be flattred the next month. This is especially true for general purpose things like what I am using currently. Others might create things for every single blog entry, or very specific tasks, to allow people to flattr them more often in a month and get a bigger share of the cake. So keep in mind which things are general ones and consider returning to them.