Flattr is a new Swedish service enabling easy microtransactions, or social donations, for the whole web. Flattr wants to make it easy for people to share money in addition to content on the web, and thus allow content producers to get income on their work. The service is currently in closed beta, but I got an account to take a closer look.
In practice, every Flattr member needs to pay at least 2 euros per month (you can up to 5/10/20 as well). Then, during each month, you discover content on the web that you really like, be it text, audio, video, or something else, and you want to "flatter" the creator. You then click a small button the content creator has placed on her site. After each month is over, your monthly allowance (e.g., 2 euros) is divided evenly to all of the content creators whose work you have "flattred" during the month. Flattr itself takes 10% cut initially.
Flattr's system encourages (or enforces) reciprocity - in order to get money from Flattr, you also need to be an active giving community member. Before you can get flattred you need to add some funds for flattring others, and if you empty your whole account you stop getting money as well. And if you do not flattr anything during a month, your allocated budget will be directed to charity.
Creating an account and adding up some funds is straight-forward. Finding content that can be flattred is naturally harder due to the limited beta phase. Flattr however collects all "Things" that can be flattred under the website (you need to create an entry for the content item on their system for tracking the clicks on that item - manually or automatically through their APIs) , where they can be easily found for now. Sharing your love is then just a matter of clicking the Flattr This! button.
The more you share and the more you flattr (or "like") things, do not cost any more to you than the monthly fee you are already paying. Thus sharing and donating should increase a lot. Also content creators could in theory get even higher income, as people who really love their work could donate multiple times instead of typical one-off payments.
This concept of recurring microdonations is actually exactly the idea Richard Stallman presented in his speech/essay Copyright and Globalization in the Age of Computer Networks in 2001. (You can also check out the edited version.)
Flattr's ideology does not fall very far, as one of the co-founders of Flattr is Peter Sunde, co-founder of the (in)famous The Pirate Bay, also a strong evangelist of civil rights in the digital world.
I see Flattr as an extremely interesting concept, one that I would definitely like to spread very wide in the web. This kind of system does require a huge critical mass, though, in order to work properly and interest the wider audience. It could also be that Facebook decides to implement something similar, now that they are building their Credits system as a ubiquitous billing platform, and allow already people to "like" pretty much all of the web.