The games, as listed on the promotion page, are World of Goo, Aquaria, Gish, Lugaru, and Penumbra. Every one of them is well-received and usually fetch $20 each. At least one (World of Goo) has a metascore of 90. They're also DRM-free and fully compatible with Windows, Mac, and Linux machines, so you're free to install them on every system you have.
While you can pay as little as a penny, the folks behind the promotion are hoping you'll dig a little deeper. Every cent goes directly to the developers as well as non-profit organizations you select, and you can customize the amount you give to each. PayPal, Amazon, and Google Checkout are all supported payment options, so just about everyone should be covered.
Thus far, the Humble Indie Bundle has collected over $500,000, with Windows users making up just over half of that revenue. The other chunk is evenly split between Mac and Linux. While Windows users have technically contributed the most, the average donation of $6.96 is lower than the other platforms. Mac users shelled out $9.69 on average, and Linux users are the most generous at $13.74.
The event only lasts for three more days so if you're interested, be sure to head over soon.