Flattr allows you to place a "click me because you appreciate me" button on your site and when somebody clicks it, you get a bit of money.
So far you had to invest at least 2€ to be part of the service. Now you can use it for free.
So every project that is a one-person project or has a donation infrastructure: please add flattr to your site.
If neiter fits: start thinking about how you would share donations with the team if you got any and add a flattr button when you're done. :)
Thanks to Grumbel for reminding via his post.