I really recommend checking out Chrome For A Cause and NogPong since those will end soon.
1) Save as a WWF, a neat way to actually save trees by not allowing people to print their docs
2) Chrome For A Cause, With every tab you open in your Google Chrome browser from today until December 19th you could donate water, books, shelter, vaccinations or trees. I've already gone psycho on the apple+Ts and currently have 15 tabs open, but guess what? I just helped provide 6 persons' worth of clean water. I am hoping Google will share the results of this project in a colorful trend graph and YouTube videos of the donations.
3) NogPong, this one is actually fun which makes it even more awesome. Saatchi & Saatchi LA created a site that streams live video of Saatchi workers responding to real-time pong throws into cups of eggnog. Anyone with an internet connection can take a shot simply by clicking (you're able to adjust the aim and strength of the throw). The charity portion is that with every cup made they will donate to selected charities. NogPong was definitely made with the user experience in mind--engagement rates must be out the roof. Good job @SaatchiLA!
What I love best about all three of these ideas is that it started with a natural consumer action e.g. saving a file, opening a tab, throwing a pong ball and tailored it to be relevant to the organization, company or agency i.e. file type = "WWF", tabs <3 browsers and Chrome is a browser, and agency holiday office parties are just fun! Plus all sites were fully equipped with Facebook and Twitter sharing functionality.
Stuff like this makes me very happy because it reassures me that humanity and this industry is still very clever and that digital is progressing in a positive direction.