The charity is The Hero Initiative which "creates a financial safety net for yesterday's creators who may need emergency medical aid, financial support for essentials of life, and an avenue back into paying work. Keep in mind even today most comic book writers, artists, inkers etc. got paid once for their work. Even if the book remains published in perpetuity in trade form, they rarely get any additional money for its sales success. Even if that work was later used to inspire TV shows, movies, and so forth. Except for maybe Stan Lee, most of the creators of the characters that you have seen in all these movies over the last decade have rarely been given one cent from those successful franchises. Its a worthy cause even if you wind up nothing reading the comics.
I recommend creating a Humble Bundle account first if you do not already have one and then log in before donating. That way your purchase is tied into your account to re-download if need to in the future. After donating you will receive an email to the site to download the comics in .cbz, .pdf, .epub and .mobi formats. Apps I recommend include ComicGlass for iPad/iPhone (uses .pdf or .cbz format), Cover for Windows 8 (.cbz), Perfect Viewer for Android (.cbz) and Play Books from Google (.epub, .mobi, .pdf). Below is the video about the promotion. For more details and place your donation/order click here or even purchase as a gift for others. The bundle ends on Wednesday, September 17th at 2pm ET.